VulnerabilityDeferred

CVE-2026-62995

This could lead to bypass of token revocation or anti-replay protection when implemented as a deny list of tokens or a deny list of token hashes.

LOW 2.3EPSS 0.11%

Does this matter?

Lower severity and a low EPSS score (0.11%). Track it; it rarely justifies an emergency change on its own.

Description

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. in versions 1.7.1 and prior, joserfc accepts JWTs with trailing padding (==) which are not conforming to the JOSE specifications. This leads to malleability of the JWTs when consumed by joserfc. Depending on this application this might or not be an issue. This could lead to bypass of token revocation or anti-replay protection when implemented as a deny list of tokens or a deny list of token hashes. Note that ECDSA JWS are always malleable because of the malleability of ECDSA signatures (first test case in the code bellow). This makes a scheme which assumes that JWTs are not malleable brittle. However for other signatures (or MAC) schemes it might make sense to assume non malleability of the token. This issue has been fixed in version 1.7.2.

CVSS 4.0: 2.3 LOWCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.11% probability · 1th percentile
CISA KEV: Not listed
Weakness: CWE-345
Source: security-advisories@github.com

References

https://github.com/authlib/joserfc/security/advisories/GHSA-5jhw-7jv7-qcqq

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.