CVE-2026-107722fast-jwt: Incomplete patch of CVE-2026-34950: Non-whitespace key-prefix re-enables RSA→HS256 algorithm confusion
Updated under an hour ago ()
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It affects nearform fast-jwt. Add what you run to find out whether that includes you.
EPSS puts the chance of exploitation in the next 30 days at 0.27%, higher than 18% of scored CVEs.
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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.
- CVSS
- 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-347
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- 0.27% (percentile 18)
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Oct 13, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
nearform fast-jwt nearform:fast_jwt (from the name) | from 6.2.0, < 6.3.0 | CNA record |
References
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-ww5h-9m49-7xx4x-refsource-confirm
- https://github.com/nearform/fast-jwt/pull/632x-refsource-misc
- https://github.com/nearform/fast-jwt/commit/d96bbc6c5336055a6dbfa318fdbab01197264cfax-refsource-misc
- https://github.com/nearform/fast-jwt/releases/tag/v6.3.0x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.