PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.prepare_key in jwt/algorithms.py is affected because raw-JWK detector does not normalize accepted Unicode byte-order marks before checking for JSON. This occurs when a public JWK is prefixed with a UTF-8 BOM and used in a mixed-algorithm verification path. As a result, public JWK bypasses asymmetric-key detection and becomes the HMAC secret. Consequently, an attacker who knows the public key can forge authenticated tokens. This issue is fixed in version 2.14.0.
Metrics
Affected Vendors & Products
References
History
Tue, 06 Oct 2026 18:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Pyjwt Project
Pyjwt Project pyjwt |
|
| CPEs | cpe:2.3:a:pyjwt_project:pyjwt:2.13.0:*:*:*:*:*:*:* | |
| Vendors & Products |
Pyjwt Project
Pyjwt Project pyjwt |
Tue, 29 Sep 2026 15:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
|
Tue, 29 Sep 2026 13:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
| |
| Metrics |
threat_severity
|
threat_severity
|
Mon, 28 Sep 2026 23:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Jpadilla
Jpadilla pyjwt |
|
| Vendors & Products |
Jpadilla
Jpadilla pyjwt |
Mon, 28 Sep 2026 21:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.prepare_key in jwt/algorithms.py is affected because raw-JWK detector does not normalize accepted Unicode byte-order marks before checking for JSON. This occurs when a public JWK is prefixed with a UTF-8 BOM and used in a mixed-algorithm verification path. As a result, public JWK bypasses asymmetric-key detection and becomes the HMAC secret. Consequently, an attacker who knows the public key can forge authenticated tokens. This issue is fixed in version 2.14.0. | |
| Title | PyJWT BOM Bypass | |
| Weaknesses | CWE-347 | |
| References |
| |
| Metrics |
cvssV3_1
|
Status: PUBLISHED
Assigner: GitHub_M
Published: 2026-09-28T20:36:31.530Z
Updated: 2026-09-29T14:45:44.138Z
Reserved: 2026-09-28T20:11:16.658Z
Link: CVE-2026-102272
Updated: 2026-09-29T14:45:22.047Z
Status : Analyzed
Published: 2026-09-28T21:17:15.280
Modified: 2026-10-06T18:34:24.710
Link: CVE-2026-102272