CVE-2026-101918

PyJWT: Unauthenticated RecursionError DoS in pre-verification payload parse (PyJWKClient.get_signing_key_from_jwt / verify_signature=False)

Description

PyJWT is a Python implementation of JSON Web Token standards. From 2.0.0a1 until 2.15.0, PyJWT PyJWKClient.get_signing_key_from_jwt is affected because payload parser catches ValueError but not RecursionError. This occurs when an attacker-controlled recursively nested payload reaches json.loads. As a result, documented PyJWT exception handling does not contain the failure. Consequently, an unauthenticated request can raise an exception that may produce an HTTP 500 response. The advisory-defined affected implementation also includes jwt/api_jwt.py, verify_signature=False. This issue is fixed in version 2.15.0.

Scores

Weaknesses (CWE)

• CWE-248

Advisories

• GHSA-42vr-xj54-vc7v — PyJWT: Unauthenticated RecursionError DoS in pre-verification payload parse (PyJWKClient.get_signing_key_from_jwt / verify_signature=False)
• PYSEC-2026-4141 — PyJWT: Unauthenticated RecursionError DoS in pre-verification payload parse (PyJWKClient.get_signing_key_from_jwt / verify_signature=False)

European references

• ENISA EUVD · EUVD-2026-88479
• GCVE · GCVE-0-2026-101918

CERT-FR advisories

• CERTFR-2026-AVI-1385 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
• CERTFR-2026-AVI-1249 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr

Affected configurations (NVD CPE)

• cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:* ≥ 2.0.0 < 2.15.0

Affected products

References

• https://github.com/jpadilla/pyjwt/security/advisories/GHSA-42vr-xj54-vc7v
• https://github.com/jpadilla/pyjwt/commit/5fde08a6cf906aa7698de2d6391d88b73006b17b
• https://github.com/jpadilla/pyjwt/releases/tag/2.15.0

Sources