Vulnerability in Jpadilla Pyjwt

CVE-2026-102270

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.

Vulnerability class: ReDoS (Regular Expression Denial of Service)

Published .

CVSS v3 metric

CVSS v3 base score 4.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-102270?
CVE-2026-102270 is a medium-severity vulnerability in Jpadilla Pyjwt, classified under Inefficient Regular Expression Complexity. CVSS score: 4.4/10. Published 2026-09-28.
How severe is CVE-2026-102270?
Medium severity. CVSS v3 base score is 4.4 out of 10.