Improper Verification of Cryptographic Signature Affecting pyjwt package, versions [,2.14.0)
Threat Intelligence
Exploit Maturity
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
Proof of Concept
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Test your applications- Snyk IDSNYK-PYTHON-PYJWT-21431293
- published22 Oct 2026
- disclosed22 Oct 2026
- credittonghuaroot (童话)
Introduced: 22 Oct 2026
New CVE NOT AVAILABLE CWE-347 (opens in a new tab)Common Weakness Enumeration (CWE) is a category system for software weaknesses
How to fix?
Upgrade pyjwt to version 2.14.0 or higher.
Overview
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature via the from_jwk function in jwt/algorithms.py, which accepts an HMAC JWK containing an empty key ("k": "") without raising an error. An attacker who can supply a JWK with an empty k value can cause tokens to be signed and verified with a zero-length HMAC secret, effectively bypassing signature security and allowing arbitrary token forgery.