CVE-2026-102271 — Pyjwt Project Pyjwt vulnerability

Vendor	Product	Version range	Fixed in
pyjwt_project	pyjwt	>= 2.4.0 < 2.14.0	2.14.0
pyjwt_project	pyjwt	>= 2.4.0 < 2.14.0	2.14.0
ubuntu	pyjwt	—	—

GHSA

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

ghsa·2026-09-29·CVSS 7.5

CVE-2026-102271 [HIGH] CWE-347 PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard ### Summary `HMACAlgorithm.prepare_key` blocks asymmetric keys from being used as HMAC secrets by searching for text markers only. It looks for `-----BEGIN` and for an `ssh-` prefix. The same key in DER form is binary ASN.1 and has neither marker, so it passes the check and is used as an HMAC secret. An application that verifies tokens with an RSA or EC public key, and also allows HS256 with that same key, can be given a forged token. The attacker signs it with the public key, which is public. This is the key confusion problem CVE-2022-29217 was filed for, reachable again through a different encoding. The reach is smaller than the original CVE. The application must already be in that misconf

VulDB

jpadilla PyJWT up to 2.13.x HMACAlgorithm HMACAlgorithm.prepare_key signature verification

vuldb·2026-09-28·CVSS 7.4

CVE-2026-102271 [HIGH] jpadilla PyJWT up to 2.13.x HMACAlgorithm HMACAlgorithm.prepare_key signature verification A vulnerability was found in jpadilla PyJWT up to 2.13.x. It has been rated as critical. The impacted element is the function HMACAlgorithm.prepare_key of the component HMACAlgorithm. This manipulation causes improper verification of cryptographic signature. This vulnerability is tracked as CVE-2026-102271. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is advised.

Ubuntu

PyJWT vulnerabilities

vendor_ubuntu·2026-10-13·CVSS 9.1

CVE-2026-102267 [CRITICAL] PyJWT vulnerabilities Title: PyJWT vulnerabilities Summary: Several security issues were fixed in PyJWT. YuSung Han discovered that PyJWT did not properly validate certain JWK keys when performing HMAC verification. An attacker could possibly use this issue to forge authentication tokens. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-102266) Rohan Das discovered that PyJWT incorrectly handled redirects when fetching key sets. A remote attacker could possibly use this issue to cause PyJWT to disclose sensitive information. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 26.04 LTS. (CVE-2026-102267) It was discovered that PyJWT incorrectly recognized certain PEM representations. An attacker who knew the public key could possibly use this issue to forge authentication tokens. This is

Red Hat

pyjwt: PyJWT: Authentication bypass via acceptance of DER public keys as HMAC secrets

vendor_redhat·2026-09-28·CVSS 7.4

CVE-2026-102271 [HIGH] CWE-347 pyjwt: PyJWT: Authentication bypass via acceptance of DER public keys as HMAC secrets pyjwt: PyJWT: Authentication bypass via acceptance of DER public keys as HMAC secrets 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. A flaw was found in PyJWT. The library fails to identify asymmetric public keys supplied in Distinguished Encoding Rules (DER) format, inadvertently treating the public data

CVE-2026-102271: 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…

Affected

CVSS provenance