CVE-2026-44523 is a critical-severity (CVSS 10) CWE-326 vulnerability in github.com/enchant97/note-mark/backend. A fix is available for github.com/enchant97/note-mark/backend — see the affected versions and patch details below.
Note Mark: JWT Secret Weakness allows Full Account Takeover via token forgery
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44523.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-44523 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/enchant97/note-mark/backendReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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.
Impact
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.
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.UnmarshalTextor 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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/enchant97/note-mark/backend | all versions | 0.0.0-20260501152247-18b587758667go get github.com/enchant97/note-mark/backend@v0.0.0-20260501152247-18b587758667 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/enchant97/note-mark/backend, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/enchant97/note-mark/backend to 0.0.0-20260501152247-18b587758667 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44523 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-44523 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-44523. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-44523 in your dependencies?
O3 Security finds CVE-2026-44523 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.