CVE-2026-75509
joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)
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.
- Record
CVE-2026-75509- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N - Weakness
- CWE-290, CWE-345
- Updated
- 2026-11-02
EUVDEUVD-2026-65138
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.
- Record
EUVD-2026-65138- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N - Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-75509- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N - Weakness
- CWE-290, CWE-345
- Updated
- 2026-11-02
OSV
joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)
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.
- Record
CVE-2026-75509- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N - Weakness
- CWE-290, CWE-345
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-75509
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.
- Record
DEBIAN-CVE-2026-75509- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-75509
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.
- Record
UBUNTU-CVE-2026-75509- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
joserfcDebian:13 |
All versions, plus listed versions 1.1.0-11.2.0-11.2.2-11.3.1-11.3.2-1 Show 18 moreShow less1.3.4-11.4.0-11.4.1-11.4.3-11.5.0-11.6.0-11.6.1-11.6.2-11.6.3-11.6.4-11.6.5-11.6.8-11.7.0-11.7.1-11.7.2-11.7.3-11.7.4-11.7.5-1 |
None known |
joserfcDebian:14 |
before 1.7.3-1, plus listed versions 1.1.0-11.2.0-11.2.2-11.3.1-11.3.2-1 Show 15 moreShow less1.3.4-11.4.0-11.4.1-11.4.3-11.5.0-11.6.0-11.6.1-11.6.2-11.6.3-11.6.4-11.6.5-11.6.8-11.7.0-11.7.1-11.7.2-1 |
1.7.3-1 |
joserfcUbuntu:26.04:LTS |
All versions, plus listed versions 1.2.2-11.4.0-11.4.1-11.4.3-11.5.0-11.6.2-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-75509 is a medium vulnerability (CVSS 6.5) in Authlib Joserfc, published August 24, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.12%, the 2nd percentile. Fixed in joserfc 1.7.3-1.
References
github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpj
nvd.nist.gov/vuln/detail/CVE-2026-75509
security-tracker.debian.org/tracker/CVE-2026-75509
ubuntu.com/security/CVE-2026-75509
cve.org/CVERecord?id=CVE-2026-75509