CVE-2026-75509joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)
Updated under an hour ago ()
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It affects authlib joserfc. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to version 1.7.3, JWTClaimsRegistry applies membership matching to list-valued iss and sub claims, allowing an array-valued iss that contains the expected issuer to pass an intended equality check and enabling issuer-validation bypass. This issue is fixed in version 1.7.3.
- CVSS
- 6.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
- Weakness (CWE)
- CWE-290, CWE-345
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Aug 25, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
authlib joserfc authlib:joserfc (from the name) | before 1.7.3 | CNA record |
References
- https://github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpjx-refsource-confirm
- https://github.com/authlib/joserfc/commit/76ee6a59bf5773c0af00b99076c5e199031f97f1x-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.