Critical Authlib Vulnerabilities Discovered in Ubuntu Affecting JWT and CSRF

• •Four critical vulnerabilities in Authlib affect Ubuntu 24.04 and 26.04 LTS.
• •Attackers can exploit these flaws to bypass authentication and perform unauthorized actions.
• •Users are advised to update their systems to the latest package versions to mitigate risks.

Multiple vulnerabilities were identified in the Authlib library used in Ubuntu systems, specifically affecting versions 24.04 LTS and 26.04 LTS. Discovered by researchers Jay Neiva, Mauro Carrillo, and Johnny Deuss, these vulnerabilities include improper validation of cryptographic keys in JWT headers (CVE-2026-27962), handling of RSA1_5 encrypted tokens (CVE-2026-28490), and failure to reject unsupported cryptographic algorithms (CVE-2026-28498). Additionally, a lack of CSRF protection in OAuth cache features (CVE-2026-41425) was noted. Attackers could exploit these vulnerabilities to forge tokens, bypass authentication, and perform unauthorized actions. Users are urged to update their systems to mitigate these risks. The vulnerabilities were disclosed on July 16, 2026, and are now being actively addressed.