by Kastro
Paper/Archive/CVE-2026-102268

CVE-2026-102268

jpadilla pyjwt — PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard

EPSS 0.2%public exploitCVSS 9.1
critical.is priorityof 100
40
CVSS 9.1 (CNA)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 14.6.146 × 202.9Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, is_pem_format in jwt/utils.py is affected because is_pem_format does not recognize every PEM representation accepted by the cryptography loader. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a mutated public-key PEM as raw key bytes. As a result, HMACAlgorithm.prepare_key treats the unrecognized asymmetric public key as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.

Affected

ProductAffectedFixed inSource
pyjwt< 2.14.0–CNA

Scores by source

GitHub_M (CNA)9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CISA ADPSSVCExploitation: poc · Automatable: yes · Technical impact: total

References

exploitgithub.com/jpadilla/pyjwt/security/advisories/GHSA-ffc3-869f-jxw9refgithub.com/jpadilla/pyjwt/commit/8b4e233a22206b34ec1186e912e75c0b2396ac07refgithub.com/jpadilla/pyjwt/releases/tag/2.14.0