CVE-2026-62995 Details
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.
A vulnerability exists in the joserfc library, which implements JSON Object Signing and Encryption (JOSE) standards. In versions through 1.7.1, the library accepts JSON Web Tokens (JWTs) with trailing padding that violate JOSE specifications. This acceptance creates a malleability issue, allowing JWTs to be altered in a way that could bypass token revocation or anti-replay protections, depending on the application's implementation. Notably, JWTs signed with ECDSA are always malleable due to the nature of ECDSA signatures, making any scheme that assumes JWTs are immutable fragile.
Users can upgrade to joserfc version 1.7.2, which addresses this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jul 29, 2026CISA-ADP
Assessed Jul 30, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/authlib/joserfc/security/advisories/GHSA-5jhw-7jv7-qcqq | [email protected] | AdvisoryExploitRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-345 | Insufficient Verification of Data Authenticity | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| authlib joserfc | <= 1.7.1 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 30, 2026 | CVE Modified | CISA-ADP |
| Jul 29, 2026 | New CVE Received | [email protected] |