Improper Verification of Cryptographic Signature Affecting pyjwt package, versions [,2.14.0)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-PYJWT-20249112
- published29 Sept 2026
- disclosed28 Sept 2026
- credite1
Introduced: 28 Sep 2026
NewCVE-2026-102268 (opens in a new tab)How to fix?
Upgrade PyJWT to version 2.14.0 or higher.
Overview
PyJWT is a Python implementation of RFC 7519.
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature via is_pem_format() in jwt/utils.py, which fails to recognize certain loader-accepted PEM formatting variants as valid PEM. The fix for CVE-2022-29217 rejects an asymmetric key passed to an HMAC algorithm only when is_pem_format() identifies the key as PEM-encoded. Because the old regex does not match all PEM variants that the underlying cryptography library's loader accepts, an attacker can supply a non-standard but loader-accepted PEM key to bypass the asymmetric-key-as-HMAC-secret guard, enabling signature forgery.
Note: This is only exploitable when the application accepts a user-influenced key or algorithm selection that allows an asymmetric public key to be used as an HMAC secret.