diff --git a/backend/internal/handler/auth_oauth_pending_flow_test.go b/backend/internal/handler/auth_oauth_pending_flow_test.go
index 91a65d5f11..dd8e1c03fe 100644
--- a/backend/internal/handler/auth_oauth_pending_flow_test.go
+++ b/backend/internal/handler/auth_oauth_pending_flow_test.go
@@ -3593,3 +3593,20 @@ func (oauthPendingFlowTotpEncryptorStub) Encrypt(plaintext string) (string, erro
 func (oauthPendingFlowTotpEncryptorStub) Decrypt(ciphertext string) (string, error) {
 	return ciphertext, nil
 }
+
+func (s *oauthPendingFlowEmailCacheStub) IncrVerificationCodeAttempts(_ context.Context, email string) (int, error) {
+	data := s.verificationCodes[email]
+	if data == nil {
+		return 0, errors.New("verification code not found")
+	}
+	data.Attempts++
+	return data.Attempts, nil
+}
+
+func (s *oauthPendingFlowEmailCacheStub) IncrNotifyVerifyCodeAttempts(context.Context, string) (int, error) {
+	return 0, errors.New("notify verification code not found")
+}
+
+func (s *oauthPendingFlowEmailCacheStub) ConsumePasswordResetToken(context.Context, string, string) (bool, error) {
+	return false, nil
+}
diff --git a/backend/internal/handler/user_handler_test.go b/backend/internal/handler/user_handler_test.go
index a40755c920..796c64f339 100644
--- a/backend/internal/handler/user_handler_test.go
+++ b/backend/internal/handler/user_handler_test.go
@@ -6,6 +6,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -811,3 +812,19 @@ func TestUserHandlerStartIdentityBindingReturnsAuthorizeURL(t *testing.T) {
 	require.Contains(t, resp.Data.AuthorizeURL, "intent=bind_current_user")
 	require.Contains(t, resp.Data.AuthorizeURL, "redirect=%2Fsettings%2Fprofile")
 }
+
+func (s *userHandlerEmailCacheStub) IncrVerificationCodeAttempts(context.Context, string) (int, error) {
+	if s.data == nil {
+		return 0, errors.New("verification code not found")
+	}
+	s.data.Attempts++
+	return s.data.Attempts, nil
+}
+
+func (s *userHandlerEmailCacheStub) IncrNotifyVerifyCodeAttempts(context.Context, string) (int, error) {
+	return 0, errors.New("notify verification code not found")
+}
+
+func (s *userHandlerEmailCacheStub) ConsumePasswordResetToken(context.Context, string, string) (bool, error) {
+	return false, nil
+}
diff --git a/backend/internal/repository/email_cache.go b/backend/internal/repository/email_cache.go
index 96a23a8ed6..9f59ff05b2 100644
--- a/backend/internal/repository/email_cache.go
+++ b/backend/internal/repository/email_cache.go
@@ -17,8 +17,42 @@ const (
 	passwordResetKeyPrefix       = "password_reset:"
 	passwordResetSentAtKeyPrefix = "password_reset_sent:"
 	notifyCodeUserRateKeyPrefix  = "notify_code_user_rate:"
+
+	// attemptsKeySuffix stores the failed-attempt counter next to a verification code.
+	// Kept in a separate key so it can be incremented atomically with INCR.
+	attemptsKeySuffix = ":attempts"
 )
 
+// incrAttemptsScript atomically increments the attempt counter for an existing
+// verification code and aligns the counter TTL with the code TTL.
+// KEYS[1] = code key, KEYS[2] = attempts key. Returns -1 when the code is missing.
+var incrAttemptsScript = redis.NewScript(`
+if redis.call('EXISTS', KEYS[1]) == 0 then
+  return -1
+end
+local n = redis.call('INCR', KEYS[2])
+local ttl = redis.call('PTTL', KEYS[1])
+if ttl > 0 then
+  redis.call('PEXPIRE', KEYS[2], ttl)
+end
+return n
+`)
+
+// consumeResetTokenScript atomically compares the stored token hash and deletes it.
+// KEYS[1] = reset key, ARGV[1] = expected token hash. Returns 1 on success, 0 otherwise.
+var consumeResetTokenScript = redis.NewScript(`
+local v = redis.call('GET', KEYS[1])
+if not v then
+  return 0
+end
+local ok, d = pcall(cjson.decode, v)
+if not ok or type(d) ~= 'table' or d['Token'] ~= ARGV[1] then
+  return 0
+end
+redis.call('DEL', KEYS[1])
+return 1
+`)
+
 // verifyCodeKey generates the Redis key for email verification code.
 // Email is lowercased for case-insensitive consistency.
 func verifyCodeKey(email string) string {
@@ -50,8 +84,7 @@ func NewEmailCache(rdb *redis.Client) service.EmailCache {
 	return &emailCache{rdb: rdb}
 }
 
-func (c *emailCache) GetVerificationCode(ctx context.Context, email string) (*service.VerificationCodeData, error) {
-	key := verifyCodeKey(email)
+func (c *emailCache) getCode(ctx context.Context, key string) (*service.VerificationCodeData, error) {
 	val, err := c.rdb.Get(ctx, key).Result()
 	if err != nil {
 		return nil, err
@@ -60,21 +93,56 @@ func (c *emailCache) GetVerificationCode(ctx context.Context, email string) (*se
 	if err := json.Unmarshal([]byte(val), &data); err != nil {
 		return nil, err
 	}
+	if n, err := c.rdb.Get(ctx, key+attemptsKeySuffix).Int(); err == nil && n > data.Attempts {
+		data.Attempts = n
+	}
 	return &data, nil
 }
 
-func (c *emailCache) SetVerificationCode(ctx context.Context, email string, data *service.VerificationCodeData, ttl time.Duration) error {
-	key := verifyCodeKey(email)
+func (c *emailCache) setCode(ctx context.Context, key string, data *service.VerificationCodeData, ttl time.Duration) error {
 	val, err := json.Marshal(data)
 	if err != nil {
 		return err
 	}
-	return c.rdb.Set(ctx, key, val, ttl).Err()
+	pipe := c.rdb.TxPipeline()
+	pipe.Set(ctx, key, val, ttl)
+	pipe.Del(ctx, key+attemptsKeySuffix)
+	if data.Attempts > 0 {
+		pipe.Set(ctx, key+attemptsKeySuffix, data.Attempts, ttl)
+	}
+	_, err = pipe.Exec(ctx)
+	return err
+}
+
+func (c *emailCache) incrCodeAttempts(ctx context.Context, key string) (int, error) {
+	n, err := incrAttemptsScript.Run(ctx, c.rdb, []string{key, key + attemptsKeySuffix}).Int()
+	if err != nil {
+		return 0, err
+	}
+	if n < 0 {
+		return 0, redis.Nil
+	}
+	return n, nil
+}
+
+func (c *emailCache) deleteCode(ctx context.Context, key string) error {
+	return c.rdb.Del(ctx, key, key+attemptsKeySuffix).Err()
+}
+
+func (c *emailCache) GetVerificationCode(ctx context.Context, email string) (*service.VerificationCodeData, error) {
+	return c.getCode(ctx, verifyCodeKey(email))
+}
+
+func (c *emailCache) SetVerificationCode(ctx context.Context, email string, data *service.VerificationCodeData, ttl time.Duration) error {
+	return c.setCode(ctx, verifyCodeKey(email), data, ttl)
+}
+
+func (c *emailCache) IncrVerificationCodeAttempts(ctx context.Context, email string) (int, error) {
+	return c.incrCodeAttempts(ctx, verifyCodeKey(email))
 }
 
 func (c *emailCache) DeleteVerificationCode(ctx context.Context, email string) error {
-	key := verifyCodeKey(email)
-	return c.rdb.Del(ctx, key).Err()
+	return c.deleteCode(ctx, verifyCodeKey(email))
 }
 
 // Password reset token methods
@@ -101,6 +169,16 @@ func (c *emailCache) SetPasswordResetToken(ctx context.Context, email string, da
 	return c.rdb.Set(ctx, key, val, ttl).Err()
 }
 
+// ConsumePasswordResetToken atomically deletes the stored reset token when its
+// stored hash equals tokenHash. Returns true only for the single winning caller.
+func (c *emailCache) ConsumePasswordResetToken(ctx context.Context, email, tokenHash string) (bool, error) {
+	n, err := consumeResetTokenScript.Run(ctx, c.rdb, []string{passwordResetKey(email)}, tokenHash).Int()
+	if err != nil {
+		return false, err
+	}
+	return n == 1, nil
+}
+
 func (c *emailCache) DeletePasswordResetToken(ctx context.Context, email string) error {
 	key := passwordResetKey(email)
 	return c.rdb.Del(ctx, key).Err()
@@ -122,30 +200,19 @@ func (c *emailCache) SetPasswordResetEmailCooldown(ctx context.Context, email st
 // Notify email verification code methods
 
 func (c *emailCache) GetNotifyVerifyCode(ctx context.Context, email string) (*service.VerificationCodeData, error) {
-	key := notifyVerifyKey(email)
-	val, err := c.rdb.Get(ctx, key).Result()
-	if err != nil {
-		return nil, err
-	}
-	var data service.VerificationCodeData
-	if err := json.Unmarshal([]byte(val), &data); err != nil {
-		return nil, err
-	}
-	return &data, nil
+	return c.getCode(ctx, notifyVerifyKey(email))
 }
 
 func (c *emailCache) SetNotifyVerifyCode(ctx context.Context, email string, data *service.VerificationCodeData, ttl time.Duration) error {
-	key := notifyVerifyKey(email)
-	val, err := json.Marshal(data)
-	if err != nil {
-		return err
-	}
-	return c.rdb.Set(ctx, key, val, ttl).Err()
+	return c.setCode(ctx, notifyVerifyKey(email), data, ttl)
+}
+
+func (c *emailCache) IncrNotifyVerifyCodeAttempts(ctx context.Context, email string) (int, error) {
+	return c.incrCodeAttempts(ctx, notifyVerifyKey(email))
 }
 
 func (c *emailCache) DeleteNotifyVerifyCode(ctx context.Context, email string) error {
-	key := notifyVerifyKey(email)
-	return c.rdb.Del(ctx, key).Err()
+	return c.deleteCode(ctx, notifyVerifyKey(email))
 }
 
 // User-level rate limiting for notify email verification codes
diff --git a/backend/internal/repository/email_cache_atomic_test.go b/backend/internal/repository/email_cache_atomic_test.go
new file mode 100644
index 0000000000..0086bbe460
--- /dev/null
+++ b/backend/internal/repository/email_cache_atomic_test.go
@@ -0,0 +1,150 @@
+package repository
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/alicebob/miniredis/v2"
+	"github.com/redis/go-redis/v9"
+	"github.com/stretchr/testify/require"
+)
+
+func newMiniredisEmailCache(t *testing.T) (service.EmailCache, *miniredis.Miniredis, *redis.Client) {
+	t.Helper()
+	mr := miniredis.RunT(t)
+	rdb := redis.NewClient(&redis.Options{Addr: mr.Addr()})
+	t.Cleanup(func() { _ = rdb.Close() })
+	return NewEmailCache(rdb), mr, rdb
+}
+
+func TestEmailCache_ConcurrentWrongCodesCannotExceedAttemptCap(t *testing.T) {
+	cache, _, _ := newMiniredisEmailCache(t)
+	ctx := context.Background()
+	email := "user@example.com"
+
+	svc := service.NewEmailService(nil, cache)
+	require.NoError(t, cache.SetVerificationCode(ctx, email, &service.VerificationCodeData{
+		Code:      "123456",
+		CreatedAt: time.Now(),
+		ExpiresAt: time.Now().Add(15 * time.Minute),
+	}, 15*time.Minute))
+
+	const workers = 50
+	var invalid, maxed atomic.Int32
+	var wg sync.WaitGroup
+	for i := 0; i < workers; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			err := svc.VerifyCode(ctx, email, "000000")
+			switch {
+			case errors.Is(err, service.ErrInvalidVerifyCode):
+				invalid.Add(1)
+			case errors.Is(err, service.ErrVerifyCodeMaxAttempts):
+				maxed.Add(1)
+			default:
+				t.Errorf("unexpected result: %v", err)
+			}
+		}()
+	}
+	wg.Wait()
+
+	// Only attempts 1..4 may return "invalid"; every other guess is rejected by the cap.
+	require.LessOrEqual(t, int(invalid.Load()), 4)
+	require.Equal(t, workers, int(invalid.Load()+maxed.Load()))
+
+	// Even the correct code is now rejected.
+	require.ErrorIs(t, svc.VerifyCode(ctx, email, "123456"), service.ErrVerifyCodeMaxAttempts)
+
+	data, err := cache.GetVerificationCode(ctx, email)
+	require.NoError(t, err)
+	require.GreaterOrEqual(t, data.Attempts, 5)
+}
+
+func TestEmailCache_AttemptsResetOnNewCodeAndTTLFollowsCode(t *testing.T) {
+	cache, mr, _ := newMiniredisEmailCache(t)
+	ctx := context.Background()
+	email := "User@Example.com"
+
+	require.NoError(t, cache.SetVerificationCode(ctx, email, &service.VerificationCodeData{Code: "1"}, time.Minute))
+	n, err := cache.IncrVerificationCodeAttempts(ctx, email)
+	require.NoError(t, err)
+	require.Equal(t, 1, n)
+	require.Greater(t, mr.TTL(verifyCodeKey(email)+attemptsKeySuffix), time.Duration(0))
+
+	require.NoError(t, cache.SetVerificationCode(ctx, email, &service.VerificationCodeData{Code: "2"}, time.Minute))
+	data, err := cache.GetVerificationCode(ctx, email)
+	require.NoError(t, err)
+	require.Equal(t, 0, data.Attempts)
+
+	require.NoError(t, cache.DeleteVerificationCode(ctx, email))
+	_, err = cache.IncrVerificationCodeAttempts(ctx, email)
+	require.Error(t, err)
+	require.False(t, mr.Exists(verifyCodeKey(email)+attemptsKeySuffix))
+}
+
+func TestEmailCache_PasswordResetTokenHashedAndSingleUse(t *testing.T) {
+	cache, mr, _ := newMiniredisEmailCache(t)
+	ctx := context.Background()
+	email := "reset@example.com"
+
+	svc := service.NewEmailService(nil, cache)
+
+	// Seed the token the same way SendPasswordResetEmail does (hash only).
+	token, err := svc.GeneratePasswordResetToken()
+	require.NoError(t, err)
+	sum := sha256.Sum256([]byte(token))
+	require.NoError(t, cache.SetPasswordResetToken(ctx, email, &service.PasswordResetTokenData{
+		Token: hex.EncodeToString(sum[:]), CreatedAt: time.Now(),
+	}, 30*time.Minute))
+
+	raw, err := mr.Get(passwordResetKey(email))
+	require.NoError(t, err)
+	require.False(t, strings.Contains(raw, token), "plaintext token must not be stored")
+
+	require.NoError(t, svc.VerifyPasswordResetToken(ctx, email, token))
+	require.ErrorIs(t, svc.ConsumePasswordResetToken(ctx, email, "wrong"), service.ErrInvalidResetToken)
+
+	const workers = 30
+	var ok atomic.Int32
+	var wg sync.WaitGroup
+	for i := 0; i < workers; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			if svc.ConsumePasswordResetToken(ctx, email, token) == nil {
+				ok.Add(1)
+			}
+		}()
+	}
+	wg.Wait()
+	require.Equal(t, int32(1), ok.Load())
+	require.False(t, mr.Exists(passwordResetKey(email)))
+}
+
+func TestEmailCache_ConsumePasswordResetTokenMismatchKeepsToken(t *testing.T) {
+	cache, mr, _ := newMiniredisEmailCache(t)
+	ctx := context.Background()
+	email := "keep@example.com"
+	require.NoError(t, cache.SetPasswordResetToken(ctx, email, &service.PasswordResetTokenData{Token: "abc"}, time.Minute))
+
+	ok, err := cache.ConsumePasswordResetToken(ctx, email, "xyz")
+	require.NoError(t, err)
+	require.False(t, ok)
+	require.True(t, mr.Exists(passwordResetKey(email)))
+
+	ok, err = cache.ConsumePasswordResetToken(ctx, email, "abc")
+	require.NoError(t, err)
+	require.True(t, ok)
+	ok, err = cache.ConsumePasswordResetToken(ctx, email, "abc")
+	require.NoError(t, err)
+	require.False(t, ok)
+}
diff --git a/backend/internal/service/auth_service_email_bind_test.go b/backend/internal/service/auth_service_email_bind_test.go
index 9bdca02f2d..c41734c40b 100644
--- a/backend/internal/service/auth_service_email_bind_test.go
+++ b/backend/internal/service/auth_service_email_bind_test.go
@@ -1165,3 +1165,19 @@ func cloneEmailBindUser(user *service.User) *service.User {
 	cloned := *user
 	return &cloned
 }
+
+func (s *emailBindCacheStub) IncrVerificationCodeAttempts(context.Context, string) (int, error) {
+	if s.data == nil {
+		return 0, errors.New("verification code not found")
+	}
+	s.data.Attempts++
+	return s.data.Attempts, nil
+}
+
+func (s *emailBindCacheStub) IncrNotifyVerifyCodeAttempts(context.Context, string) (int, error) {
+	return 0, errors.New("notify verification code not found")
+}
+
+func (s *emailBindCacheStub) ConsumePasswordResetToken(context.Context, string, string) (bool, error) {
+	return false, nil
+}
diff --git a/backend/internal/service/auth_service_register_test.go b/backend/internal/service/auth_service_register_test.go
index aa7519f3d1..076cd025d3 100644
--- a/backend/internal/service/auth_service_register_test.go
+++ b/backend/internal/service/auth_service_register_test.go
@@ -1010,3 +1010,19 @@ func TestCanBypassRegistrationDisabledForOAuth(t *testing.T) {
 		})
 	}
 }
+
+func (s *emailCacheStub) IncrVerificationCodeAttempts(context.Context, string) (int, error) {
+	if s.data == nil {
+		return 0, errors.New("verification code not found")
+	}
+	s.data.Attempts++
+	return s.data.Attempts, nil
+}
+
+func (s *emailCacheStub) IncrNotifyVerifyCodeAttempts(context.Context, string) (int, error) {
+	return 0, errors.New("notify verification code not found")
+}
+
+func (s *emailCacheStub) ConsumePasswordResetToken(context.Context, string, string) (bool, error) {
+	return false, nil
+}
diff --git a/backend/internal/service/email_service.go b/backend/internal/service/email_service.go
index 8e60d9e73d..794dad5258 100644
--- a/backend/internal/service/email_service.go
+++ b/backend/internal/service/email_service.go
@@ -3,6 +3,7 @@ package service
 import (
 	"context"
 	"crypto/rand"
+	"crypto/sha256"
 	"crypto/subtle"
 	"crypto/tls"
 	"crypto/x509"
@@ -37,16 +38,23 @@ type EmailCache interface {
 	GetVerificationCode(ctx context.Context, email string) (*VerificationCodeData, error)
 	SetVerificationCode(ctx context.Context, email string, data *VerificationCodeData, ttl time.Duration) error
 	DeleteVerificationCode(ctx context.Context, email string) error
+	// IncrVerificationCodeAttempts atomically increments the attempt counter of an
+	// existing code and returns the new count. Returns an error if the code is missing.
+	IncrVerificationCodeAttempts(ctx context.Context, email string) (int, error)
 
 	// Notify email verification code methods
 	GetNotifyVerifyCode(ctx context.Context, email string) (*VerificationCodeData, error)
 	SetNotifyVerifyCode(ctx context.Context, email string, data *VerificationCodeData, ttl time.Duration) error
 	DeleteNotifyVerifyCode(ctx context.Context, email string) error
+	IncrNotifyVerifyCodeAttempts(ctx context.Context, email string) (int, error)
 
 	// Password reset token methods
 	GetPasswordResetToken(ctx context.Context, email string) (*PasswordResetTokenData, error)
 	SetPasswordResetToken(ctx context.Context, email string, data *PasswordResetTokenData, ttl time.Duration) error
 	DeletePasswordResetToken(ctx context.Context, email string) error
+	// ConsumePasswordResetToken atomically compares the stored token hash with
+	// tokenHash and deletes it on match. Only one concurrent caller can succeed.
+	ConsumePasswordResetToken(ctx context.Context, email, tokenHash string) (bool, error)
 
 	// Password reset email cooldown methods
 	// Returns true if in cooldown period (email was sent recently)
@@ -68,6 +76,7 @@ type VerificationCodeData struct {
 
 // PasswordResetTokenData represents password reset token data
 type PasswordResetTokenData struct {
+	// Token holds the hex-encoded SHA-256 hash of the reset token (never the plaintext).
 	Token     string
 	CreatedAt time.Time
 }
@@ -376,35 +385,49 @@ func (s *EmailService) SendVerifyCode(ctx context.Context, email, siteName strin
 
 // VerifyCode 验证验证码
 func (s *EmailService) VerifyCode(ctx context.Context, email, code string) error {
-	data, err := s.cache.GetVerificationCode(ctx, email)
+	return verifyCodeWithAttempts(ctx, email, code,
+		s.cache.GetVerificationCode, s.cache.IncrVerificationCodeAttempts,
+		func() {
+			if err := s.cache.DeleteVerificationCode(ctx, email); err != nil {
+				slog.Error("failed to delete verification code after success", "email", email, "error", err)
+			}
+		})
+}
+
+// verifyCodeWithAttempts checks a verification code while enforcing the attempt cap
+// atomically: each check first reserves an attempt via an atomic increment, so
+// concurrent guesses can never evaluate more than maxVerifyCodeAttempts codes.
+func verifyCodeWithAttempts(
+	ctx context.Context, email, code string,
+	get func(context.Context, string) (*VerificationCodeData, error),
+	incr func(context.Context, string) (int, error),
+	onSuccess func(),
+) error {
+	data, err := get(ctx, email)
 	if err != nil || data == nil {
 		return ErrInvalidVerifyCode
 	}
-
-	// 检查是否已达到最大尝试次数
 	if data.Attempts >= maxVerifyCodeAttempts {
 		return ErrVerifyCodeMaxAttempts
 	}
+	attempts, err := incr(ctx, email)
+	if err != nil {
+		return ErrInvalidVerifyCode
+	}
+	if attempts > maxVerifyCodeAttempts {
+		return ErrVerifyCodeMaxAttempts
+	}
 
-	// 验证码不匹配 (constant-time comparison to prevent timing attacks)
+	// constant-time comparison to prevent timing attacks
 	if subtle.ConstantTimeCompare([]byte(data.Code), []byte(code)) != 1 {
-		data.Attempts++
-		remaining := time.Until(data.ExpiresAt)
-		if remaining <= 0 {
-			return ErrInvalidVerifyCode
-		}
-		if err := s.cache.SetVerificationCode(ctx, email, data, remaining); err != nil {
-			slog.Error("failed to update verification attempt count", "email", email, "error", err)
-		}
-		if data.Attempts >= maxVerifyCodeAttempts {
+		if attempts >= maxVerifyCodeAttempts {
 			return ErrVerifyCodeMaxAttempts
 		}
 		return ErrInvalidVerifyCode
 	}
 
-	// 验证成功，删除验证码
-	if err := s.cache.DeleteVerificationCode(ctx, email); err != nil {
-		slog.Error("failed to delete verification code after success", "email", email, "error", err)
+	if onSuccess != nil {
+		onSuccess()
 	}
 	return nil
 }
@@ -480,33 +503,18 @@ func (s *EmailService) GeneratePasswordResetToken() (string, error) {
 
 // SendPasswordResetEmail sends a password reset email with a reset link
 func (s *EmailService) SendPasswordResetEmail(ctx context.Context, email, siteName, resetURL string, locale ...string) error {
-	var token string
-	var needSaveToken bool
-
-	// Check if token already exists
-	existing, err := s.cache.GetPasswordResetToken(ctx, email)
-	if err == nil && existing != nil {
-		// Token exists, reuse it (allows resending email without generating new token)
-		token = existing.Token
-		needSaveToken = false
-	} else {
-		// Generate new token
-		token, err = s.GeneratePasswordResetToken()
-		if err != nil {
-			return fmt.Errorf("generate token: %w", err)
-		}
-		needSaveToken = true
+	// Only the SHA-256 hash of the token is stored, so an existing token cannot be
+	// re-sent; always issue a fresh token (the email cooldown bounds resend frequency).
+	token, err := s.GeneratePasswordResetToken()
+	if err != nil {
+		return fmt.Errorf("generate token: %w", err)
 	}
-
-	// Save token to Redis (only if new token generated)
-	if needSaveToken {
-		data := &PasswordResetTokenData{
-			Token:     token,
-			CreatedAt: time.Now(),
-		}
-		if err := s.cache.SetPasswordResetToken(ctx, email, data, passwordResetTokenTTL); err != nil {
-			return fmt.Errorf("save reset token: %w", err)
-		}
+	data := &PasswordResetTokenData{
+		Token:     hashPasswordResetToken(token),
+		CreatedAt: time.Now(),
+	}
+	if err := s.cache.SetPasswordResetToken(ctx, email, data, passwordResetTokenTTL); err != nil {
+		return fmt.Errorf("save reset token: %w", err)
 	}
 
 	// Build full reset URL with URL-encoded token and email
@@ -566,31 +574,40 @@ func (s *EmailService) SendPasswordResetEmailWithCooldown(ctx context.Context, e
 	return nil
 }
 
+// hashPasswordResetToken returns the hex-encoded SHA-256 of a reset token.
+func hashPasswordResetToken(token string) string {
+	sum := sha256.Sum256([]byte(token))
+	return hex.EncodeToString(sum[:])
+}
+
 // VerifyPasswordResetToken verifies the password reset token without consuming it
 func (s *EmailService) VerifyPasswordResetToken(ctx context.Context, email, token string) error {
 	data, err := s.cache.GetPasswordResetToken(ctx, email)
-	if err != nil || data == nil {
+	if err != nil || data == nil || token == "" {
 		return ErrInvalidResetToken
 	}
 
 	// Use constant-time comparison to prevent timing attacks
-	if subtle.ConstantTimeCompare([]byte(data.Token), []byte(token)) != 1 {
+	if subtle.ConstantTimeCompare([]byte(data.Token), []byte(hashPasswordResetToken(token))) != 1 {
 		return ErrInvalidResetToken
 	}
 
 	return nil
 }
 
-// ConsumePasswordResetToken verifies and deletes the token (one-time use)
+// ConsumePasswordResetToken verifies and deletes the token atomically (one-time use).
 func (s *EmailService) ConsumePasswordResetToken(ctx context.Context, email, token string) error {
-	// Verify first
+	// Constant-time pre-check in Go; the atomic compare-and-delete below is authoritative.
 	if err := s.VerifyPasswordResetToken(ctx, email, token); err != nil {
 		return err
 	}
-
-	// Delete after verification (one-time use)
-	if err := s.cache.DeletePasswordResetToken(ctx, email); err != nil {
-		slog.Error("failed to delete password reset token after consumption", "email", email, "error", err)
+	ok, err := s.cache.ConsumePasswordResetToken(ctx, email, hashPasswordResetToken(token))
+	if err != nil {
+		slog.Error("failed to consume password reset token", "email", email, "error", err)
+		return ErrInvalidResetToken
+	}
+	if !ok {
+		return ErrInvalidResetToken
 	}
 	return nil
 }
diff --git a/backend/internal/service/email_service_reset_token_test.go b/backend/internal/service/email_service_reset_token_test.go
new file mode 100644
index 0000000000..15efd50d6e
--- /dev/null
+++ b/backend/internal/service/email_service_reset_token_test.go
@@ -0,0 +1,50 @@
+//go:build unit
+
+package service
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+type resetTokenCacheStub struct {
+	emailCacheStub
+	stored       *PasswordResetTokenData
+	consumedHash string
+}
+
+func (s *resetTokenCacheStub) GetPasswordResetToken(context.Context, string) (*PasswordResetTokenData, error) {
+	return s.stored, nil
+}
+
+func (s *resetTokenCacheStub) ConsumePasswordResetToken(_ context.Context, _ string, tokenHash string) (bool, error) {
+	s.consumedHash = tokenHash
+	if s.stored == nil || s.stored.Token != tokenHash {
+		return false, nil
+	}
+	s.stored = nil
+	return true, nil
+}
+
+func TestConsumePasswordResetToken_ComparesHashNotPlaintext(t *testing.T) {
+	token := "deadbeef"
+	sum := sha256.Sum256([]byte(token))
+	hash := hex.EncodeToString(sum[:])
+	require.Equal(t, hash, hashPasswordResetToken(token))
+	require.NotEqual(t, token, hashPasswordResetToken(token))
+
+	cache := &resetTokenCacheStub{stored: &PasswordResetTokenData{Token: hash}}
+	svc := NewEmailService(nil, cache)
+
+	require.NoError(t, svc.ConsumePasswordResetToken(context.Background(), "a@b.c", token))
+	require.Equal(t, hash, cache.consumedHash)
+	require.ErrorIs(t, svc.ConsumePasswordResetToken(context.Background(), "a@b.c", token), ErrInvalidResetToken)
+
+	// A legacy plaintext value (issued before upgrade) no longer validates.
+	cache.stored = &PasswordResetTokenData{Token: token}
+	require.ErrorIs(t, svc.ConsumePasswordResetToken(context.Background(), "a@b.c", token), ErrInvalidResetToken)
+}
diff --git a/backend/internal/service/user_service.go b/backend/internal/service/user_service.go
index ee9a7f257f..e6d4e50736 100644
--- a/backend/internal/service/user_service.go
+++ b/backend/internal/service/user_service.go
@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 	"crypto/sha256"
-	"crypto/subtle"
 	"encoding/base64"
 	"encoding/hex"
 	"fmt"
@@ -1318,28 +1317,7 @@ func (s *UserService) VerifyAndAddNotifyEmail(ctx context.Context, userID int64,
 
 // verifyNotifyCode validates the verification code against the cached data.
 func verifyNotifyCode(ctx context.Context, cache EmailCache, email, code string) error {
-	data, err := cache.GetNotifyVerifyCode(ctx, email)
-	if err != nil || data == nil {
-		return ErrInvalidVerifyCode
-	}
-	if data.Attempts >= maxVerifyCodeAttempts {
-		return ErrVerifyCodeMaxAttempts
-	}
-	if subtle.ConstantTimeCompare([]byte(data.Code), []byte(code)) != 1 {
-		data.Attempts++
-		remaining := time.Until(data.ExpiresAt)
-		if remaining <= 0 {
-			return ErrInvalidVerifyCode
-		}
-		if err := cache.SetNotifyVerifyCode(ctx, email, data, remaining); err != nil {
-			slog.Error("failed to update notify verify code attempts", "email", email, "error", err)
-		}
-		if data.Attempts >= maxVerifyCodeAttempts {
-			return ErrVerifyCodeMaxAttempts
-		}
-		return ErrInvalidVerifyCode
-	}
-	return nil
+	return verifyCodeWithAttempts(ctx, email, code, cache.GetNotifyVerifyCode, cache.IncrNotifyVerifyCodeAttempts, nil)
 }
 
 // addOrVerifyNotifyEmail adds the email to user's extra notification emails or marks it as verified.