CVE-2026-102268: CWE-347: Improper Verification of Cryptographic Signature in jpadilla pyjwt
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.
AI Analysis
Technical Summary
PyJWT, a Python library for JSON Web Token standards, has a cryptographic signature verification vulnerability (CWE-347) in versions before 2.14.0. The function is_pem_format does not recognize all PEM representations accepted by the cryptography loader. When applications mix HMAC and asymmetric algorithms and supply a mutated public-key PEM as raw key bytes, HMACAlgorithm.prepare_key treats the unrecognized asymmetric public key as an HMAC secret. This allows an attacker with knowledge of the public key to forge authenticated HMAC tokens. The vulnerability is addressed in PyJWT version 2.14.0.
Potential Impact
An attacker who knows the public key can forge authenticated HMAC tokens, potentially bypassing authentication controls. This compromises the integrity and authenticity of tokens, leading to unauthorized access or actions within applications relying on PyJWT for token verification.
Mitigation Recommendations
Upgrade PyJWT to version 2.14.0 or later, where this vulnerability is fixed. No other mitigations are indicated by the vendor advisory.
CVE-2026-102268: CWE-347: Improper Verification of Cryptographic Signature in jpadilla pyjwt
Description
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.
CVSS v3.1
Score 9.1critical
Affected software
jpadilla
pyjwt
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
PyJWT, a Python library for JSON Web Token standards, has a cryptographic signature verification vulnerability (CWE-347) in versions before 2.14.0. The function is_pem_format does not recognize all PEM representations accepted by the cryptography loader. When applications mix HMAC and asymmetric algorithms and supply a mutated public-key PEM as raw key bytes, HMACAlgorithm.prepare_key treats the unrecognized asymmetric public key as an HMAC secret. This allows an attacker with knowledge of the public key to forge authenticated HMAC tokens. The vulnerability is addressed in PyJWT version 2.14.0.
Potential Impact
An attacker who knows the public key can forge authenticated HMAC tokens, potentially bypassing authentication controls. This compromises the integrity and authenticity of tokens, leading to unauthorized access or actions within applications relying on PyJWT for token verification.
Mitigation Recommendations
Upgrade PyJWT to version 2.14.0 or later, where this vulnerability is fixed. No other mitigations are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-09-28T20:11:16.658Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6abad292f7a7c541062fe5ba
Added to database: 09/28/2026, 20:48:18 UTC
Last enriched: 09/28/2026, 21:02:44 UTC
Last updated: 09/29/2026, 02:48:26 UTC
Views: 8
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