6.5
MediumCVSS 3.1 · from GitHub_M
CVE-2026-75509
joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)
joserfc · CWE-290 · CWE-290Affectedjoserfc
FixNo fix listed yet.
PublishedAug 24, 20:08 · GitHub_M
ScoredAug 24 · 6.5 · GitHub_M
Exploit code publicNone known · checked 21:18 UTC
ExploitedNone known · CISA KEV checked 22:09 UTC
What we know
No known exploitation. CISA KEV, checked 22:09 UTC.
No public exploit code known. Exploit-DB, Metasploit, Nuclei, checked 21:18 UTC.
An attacker only needs network access to the target. No login needed. CVSS: network, no privileges.
It only works under certain conditions, which makes it harder to pull off. CVSS: high attack complexity.
A successful attack can change data. CVSS impact.
Description
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to version 1.7.3, JWTClaimsRegistry applies membership matching to list-valued iss and sub claims, allowing an array-valued iss that contains the expected issuer to pass an intended equality check and enabling issuer-validation bypass. This issue is fixed in version 1.7.3.
From GitHub_M
Affected and fixed versions
ProductAffectedFixed injoserfc< 1.7.3–
Exploit code
Exploit-DBnone knownMetasploitnone knownNucleinone known