CVE-2026-44523

No minimum length or entropy is enforced on the JWT_SECRET configuration value. The application accepts any base64-decodable secret regardless of size, including secrets as short as 1 byte.

HS256 secrets below 32 bytes are brute-forceable offline, allowing attackers to recover the signing key and forge valid JWTs for arbitrary users.

Details

In backend/config/utils.go, the Base64Decoded.UnmarshalText function decodes the JWT secret but does not validate its length or entropy.

In backend/core/auth.go, JWT tokens are signed using HS256 without enforcing minimum key size requirements.

According to RFC 7518 Section 3.2, HS256 keys must be at least 256 bits (32 bytes). Libraries such as PyJWT explicitly warn against shorter keys, but note-mark performs no such validation.

PoC

1- Deploy note-mark with a weak secret:

JWT_SECRET = base64("testsecret123456789012345")

2- Register an account and capture the Auth-Session-Token cookie

3- Crack the secret offline (example using Python):

import jwt, base64
jwt.decode(TOKEN, base64.b64decode(SECRET), algorithms=["HS256"])

4- Forge a new token for any user UUID with extended expiry

5- Send the forged token in requests → server returns 200 Ok and authenticates as that user

Reproduction Steps

1- Deploy the application with a JWT secret shorter than 32 bytes (after base64 decoding)
2- Authenticate and capture a valid JWT
3- Perform offline brute-force or dictionary attack against the token signature
4- Recover the secret
5- Generate a forged JWT for another user
6- Use the forged token to access protected endpoints

Fix Recommendation

• Enforce a minimum of 32 bytes (256 bits) for JWT secrets after base64 decoding
• Reject weak secrets during configuration parsing (e.g., in Base64Decoded.UnmarshalText or config validation)
• Optionally log warnings or fail startup if the secret is insecure

Resources

• RFC 7518 Section 3.2 (JSON Web Algorithms - HMAC key size requirements)
• CWE-326: Inadequate Encryption Strength
• CWE-345: Insufficient Verification of Data Authenticity

An attacker who captures a single valid JWT (e.g, from cookies, logs, or network traffic) can:

> Crack the signing secret offline using brute-force or wordlist attacks
> Forge valid JWTs for any user ID (including administrators)
> Authenticate without knowing any credentials

This results in full account takeover across the entire application with no server-side detection or rate limiting possible.

CVE-2026-44523 has a CVSS score of 10.0 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.0.0-20260501152247-18b587758667); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44523? CVE-2026-44523 is a critical-severity security vulnerability in github.com/enchant97/note-mark/backend (go), affecting versions < 0.0.0-20260501152247-18b587758667. It is fixed in 0.0.0-20260501152247-18b587758667.
2. How severe is CVE-2026-44523? CVE-2026-44523 has a CVSS score of 10.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/enchant97/note-mark/backend are affected by CVE-2026-44523? github.com/enchant97/note-mark/backend (go) versions < 0.0.0-20260501152247-18b587758667 is affected.
4. Is there a fix for CVE-2026-44523? Yes. CVE-2026-44523 is fixed in 0.0.0-20260501152247-18b587758667. Upgrade to this version or later.
5. Is CVE-2026-44523 exploitable, and should I be worried? Whether CVE-2026-44523 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44523 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44523? Upgrade github.com/enchant97/note-mark/backend to 0.0.0-20260501152247-18b587758667 or later.