CVE-2026-107722 fast-jwt: Incomplete patch of CVE-2026-34950: Non-whitespace key-prefix re-enables RSA→HS256 algorithm confusion
Attackers can bypass authentication by exploiting algorithm confusion in fast-jwt when public keys have non-whitespace prefixes, allowing HS256 token forgery.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-107722?
CVE-2026-107722 is a critical authentication bypass vulnerability in nearform fast-jwt, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
fast-jwt provides fast JSON Web Token (JWT) implementation. From 6.2.0 until 6.3.0, fast-jwt can misclassify RSA public-key text as an HMAC secret when the key has non-whitespace content before its PEM header. In src/crypto.js, performDetectPublicKeyAlgorithms trims whitespace but publicKeyPemMatcher remains start-anchored, so comments, control characters, zero-width characters, or wrapper text can prevent PEM detection and reach the HMAC fallback. An attacker who knows the public key bytes can sign arbitrary HS256 claims with that public material when HS256 is inferred or allowed, resulting in authentication or authorization bypass. An asymmetric-only algorithm allowlist prevents the attack. This issue is fixed in version 6.3.0.
Weakness: CWE-347
Which versions are affected by CVE-2026-107722?
2 open source packages ship an affected version, including fast-jwt.
| Package | Affected | Fixed in |
|---|---|---|
fast-jwt npm | From 6.2.0 | 6.3.0 |
fast-jwt npm | From 6.2.0 | 6.3.0 |
How do I fix CVE-2026-107722?
Upgrade fast-jwt to 6.3.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-107722 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-107722 exists.
Sources
Also known as GHSA-ww5h-9m49-7xx4.