diff --git a/internal/auth/auth.go b/internal/auth/auth.go
index f311c0c..e75d6aa 100644
--- a/internal/auth/auth.go
+++ b/internal/auth/auth.go
@@ -40,7 +40,15 @@ func HashPassword(password string) (string, error) {
 	), nil
 }
 
-// VerifyPassword 按 PHC 串内参数重派生并常量时间比较。任何解析失败均返回 false。
+// PHC 参数上下界（防畸形哈希触发 argon2 panic 或 OOM，评审 round2 P2-8）：
+// t/p 过小使 argon2.IDKey panic，m 过大直接耗尽内存。
+const (
+	maxArgonTime    = 10
+	maxArgonThreads = 8
+	maxArgonMemory  = 1 << 20 // KiB（1 GiB），远大于现行 19456
+)
+
+// VerifyPassword 按 PHC 串内参数重派生并常量时间比较。任何解析失败或参数越界均返回 false。
 func VerifyPassword(encoded, password string) bool {
 	parts := strings.Split(encoded, "$")
 	// ["", "argon2id", "v=19", "m=..,t=..,p=..", salt, hash]
@@ -57,12 +65,16 @@ func VerifyPassword(encoded, password string) bool {
 	if _, err := fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &m, &t, &p); err != nil {
 		return false
 	}
+	if t < 1 || t > maxArgonTime || p < 1 || p > maxArgonThreads ||
+		m < 8 || m > maxArgonMemory {
+		return false
+	}
 	salt, err := base64.RawStdEncoding.DecodeString(parts[4])
 	if err != nil {
 		return false
 	}
 	want, err := base64.RawStdEncoding.DecodeString(parts[5])
-	if err != nil {
+	if err != nil || len(want) != KeyLen {
 		return false
 	}
 	got := argon2.IDKey([]byte(password), salt, t, m, p, uint32(len(want)))
diff --git a/internal/auth/auth_test.go b/internal/auth/auth_test.go
index ced23c0..58de392 100644
--- a/internal/auth/auth_test.go
+++ b/internal/auth/auth_test.go
@@ -31,6 +31,26 @@ func TestPasswordHashRoundtrip(t *testing.T) {
 	}
 }
 
+// TestVerifyPasswordMalformedParams 畸形 PHC 参数安全返回 false：
+// t/p=0 会使 argon2.IDKey panic、m 巨大会 OOM（评审 round2 P2-8）。
+func TestVerifyPasswordMalformedParams(t *testing.T) {
+	salt := "AAAAAAAAAAAAAAAAAAAAAA"  // 16 字节 base64(raw std)
+	hash := "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA" // 32 字节
+	bad := []string{
+		"$argon2id$v=19$m=19456,t=0,p=1$" + salt + "$" + hash,
+		"$argon2id$v=19$m=19456,t=2,p=0$" + salt + "$" + hash,
+		"$argon2id$v=19$m=999999999,t=2,p=1$" + salt + "$" + hash,
+		"$argon2id$v=19$m=19456,t=999,p=1$" + salt + "$" + hash,
+		"$argon2id$v=19$m=19456,t=2,p=99$" + salt + "$" + hash,
+		"$argon2id$v=19$m=19456,t=2,p=1$" + salt + "$AAAA", // 哈希长度异常
+	}
+	for _, h := range bad {
+		if VerifyPassword(h, "x") {
+			t.Errorf("畸形参数不应通过: %s", h)
+		}
+	}
+}
+
 func TestTokenAndStrength(t *testing.T) {
 	tok, err := NewToken()
 	if err != nil {