What’s Vulnerable › Vulnerabilities

CVE-2026-101918: PyJWT: Unauthenticated RecursionError DoS in pre-verification payload parse (PyJWKClient.get_signing_key_from_jwt / verify_signature=False)

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-09-28 · updated 2026-10-07
• Weakness: CWE-248

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.

Affected products

• jpadilla pyjwt: from 2.0.0 before 2.15.0 — fixed in 2.15.0

How to fix

Upgrade to a fixed version: jpadilla pyjwt 2.15.0. Check the vendor advisory for mitigations.

References

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

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