CVE-2026-102266PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
Updated under an hour ago ()
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It affects jpadilla pyjwt and 1 other product. Add what you run to find out whether that includes you.
EPSS puts the chance of exploitation in the next 30 days at 0.18%, higher than 7% of scored CVEs.
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PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.
- CVSS
- 7.4 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weakness (CWE)
- CWE-347
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- 0.18% (percentile 7)
- Assigned by
- GitHub_M
- NVD analysis
- Analyzed
- Record last updated
- Sep 29, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
jpadilla pyjwt jpadilla:pyjwt (from the name) | from 2.13.0, < 2.14.0 | CNA record |
pyjwt_project pyjwt pyjwt_project:pyjwt | 2.13.0 | NVD |
References
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-9j54-fg26-wv3rx-refsource-confirm, exploit, vendor-advisory
- https://github.com/jpadilla/pyjwt/commit/f91ed44dd65baaf457f4b3353ed35e98a753934cx-refsource-misc, patch
- https://github.com/jpadilla/pyjwt/releases/tag/2.14.0x-refsource-misc, product, release-notes
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.