Description
PyJWT is a Python implementation of JSON Web Token standards. From 2.11.0 through 2.13.0, PyJWT's PyJWT._merge_options() method can modify a caller-supplied mutable options mapping when verify_signature is false. If an application reuses that same mapping for a later decode() or decode_complete() call and changes verify_signature to true, the mapping can retain false values for expiration, not-before, issued-at, audience, issuer, subject, and JWT ID checks. A signed token with invalid registered claims can then be accepted without disabling signature verification, but applications that create a fresh options mapping for each call are not affected.
Affected products
pyjwt_project: pyjwt
References4
- github.com/jpadilla/pyjwt/security/advisories/GHSA-gvp8-978c-rx… ExploitMitigationVendor Advisory
- github.com/jpadilla/pyjwt/security/advisories/GHSA-gvp8-978c-rx… ExploitMitigationVendor Advisory
- github.com/jpadilla/pyjwt/commit/0c87c8c8b1a74cac99ad8115f3050e… Patch
- github.com/jpadilla/pyjwt/issues/679 ExploitIssue Tracking
Metrics
- CVSS 3.1
-
6.5
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N - EPSS — exploit probability
- 0% percentile: 17 · as of 10 November 2026
- CWE
- CWE-471
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.