CVE-2026-102270
Received Received - Intake

PyJWT Unbounded Regex Backtracking DoS via Malformed PEM

Publication date: 2026-09-28

Last updated on: 2026-09-28

Assigner: GitHub, Inc.

Description
PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, PyJWT is_pem_format is affected because lazy PEM regular expression backtracks extensively. This occurs when a certificate-like input contains repeated BEGIN markers without a matching END marker. As a result, is_pem_format performs unbounded backtracking while searching for a PEM end marker. Consequently, an attacker can cause intensive CPU consumption. This issue is fixed in version 2.14.0.

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Meta Information

Published
2026-09-28
Last Modified
2026-09-28
Generated
2026-09-29
AI Q&A
2026-09-29
EPSS Evaluated
N/A
NVD
CVE-2026-102270

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
pyjwt pyjwt 2.14.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-1333 The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.

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Executive Summary

PyJWT before 2.14.0 has a vulnerability in the is_pem_format function due to a lazy regular expression that causes extensive backtracking when processing certificate-like inputs with repeated BEGIN markers but no matching END markers. This leads to high CPU usage.

Detection Guidance

To detect this vulnerability, check if your PyJWT version is below 2.14.0. Run: pip show pyjwt. If the version is older, the system is vulnerable.

Impact Analysis

An attacker could exploit this to cause denial of service by consuming excessive CPU resources, potentially slowing down or crashing systems using affected PyJWT versions.

Compliance Impact

This vulnerability could impact compliance by causing service disruptions due to CPU exhaustion, potentially violating availability requirements in GDPR or HIPAA.

Mitigation Strategies

Upgrade PyJWT to version 2.14.0 or later immediately. Use: pip install --upgrade pyjwt. Avoid processing untrusted certificate-like inputs with is_pem_format.

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