CVE-2026-62995 (GCVE-0-2026-62995)

Vulnerability from cvelistv5 – Published: 2026-07-29 18:27 – Updated: 2026-07-30 14:32
VLAI
Title
joserfc accepts JWT with padding, leading to JWT malleability
Summary
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.
Severity
2.3 (Low)
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: yes Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-30 14:31 UTC
CWE
  • CWE-345 - Insufficient Verification of Data Authenticity
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7994 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
authlib joserfc Affected: < 1.7.2
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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