Medium severity · published Sep 28, 2026
CVE-2026-102270
PyJWT: ReDoS vulnerability when calling the `is_pem_format` function.
4.9
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 16% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PY
pyjwt · jpadilla
< 2.14.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-102270
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-102270
x_refsource_CONFIRM
https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jwrc-g2q2-pq5p
x_refsource_MISC
https://github.com/jpadilla/pyjwt/commit/8b4e233a22206b34ec1186e912e75c0b2396ac07
x_refsource_MISC
https://github.com/jpadilla/pyjwt/releases/tag/2.14.0
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