CVE-2026-102271

PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard

Description

PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes 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.

Scores

Weaknesses (CWE)

• CWE-347

Advisories

• GHSA-p4g4-x82p-q773 — PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard
• PYSEC-2026-4149 — PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard

European references

• ENISA EUVD · EUVD-2026-88539
• GCVE · GCVE-0-2026-102271

CERT-FR advisories

• CERTFR-2026-AVI-1385 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
• CERTFR-2026-AVI-1249 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr

Affected configurations (NVD CPE)

• cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:* ≥ 2.4.0 < 2.14.0

Affected products

References

• https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773
• https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499
• https://github.com/jpadilla/pyjwt/releases/tag/2.14.0

Sources