A critical vulnerability in Apache Tomcat (CVE-2026-41293, CVSS 9.8) allows remote attackers to cause a crash or execute arbitrary code via malformed HTTP/2 header fields. Affected versions include Tomcat 8.5.0 through 8.5.100, 9.0.0 before 9.0.118, 10.1.0 before 10.1.55, and 11.0.0 before 11.0.22. The flaw is remediated by upgrading to Tomcat 9.0.118, 10.1.55, or 11.0.22.
It was discovered that Tomcat did not properly limit the size of WebDAV LOCK and PROPFIND request bodies. A remote attacker could use this issue to cause Tomcat to consume excessive memory, resulting in a denial of service. (CVE-2026-41284) It was discovered that Tomcat incorrectly validated HTTP/2 header fields. A remote attacker could use this issue to cause Tomcat to crash or possibly execute arbitrary code. (CVE-2026-41293) It was discovered that Tomcat did not properly clear HTTP authentication headers during WebSocket connection upgrades and redirects. A remote attacker could use this issue to obtain sensitive credentials. (CVE-2026-42498) It was discovered that Tomcat incorrectly handled digest authentication. A remote attacker could possibly use this issue to bypass authentication restrictions. (CVE-2026-43512) It was discovered that Tomcat incorrectly handled case sensitivity in LockOutRealm. A remote attacker could possibly use this issue to bypass account lockout protections and obtain sensitive information. (CVE-2026-43513) It was discovered that Tomcat incorrectly handled authorization when multiple method constraints defined the same HTTP method. A remote attacker could possibly use this issue to bypass authorization restrictions. (CVE-2026-43515)