CVE-2026-43513 Apache Tomcat: LockOutRealm treats user names as case-sensitive
Attackers can bypass account lockout mechanisms by exploiting case sensitivity in user names, allowing continued brute-force attempts against locked accounts.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43513?
CVE-2026-43513 is a high-severity authentication bypass vulnerability in Apache Tomcat, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Improper Handling of Case Sensitivity vulnerability in LockOutRealm in Apache Tomcat.
This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.21, from 10.1.0-M1 through 10.1.54, from 9.0.0.M1 through 9.0.117, from 8.5.0 through 8.5.100, from 7.0.0 through 7.0.109. Older unsupported versions may also be affected.
Users are recommended to upgrade to version 11.0.22, 10.1.55 or 9.0.118 which fix the issue.
Weakness: CWE-178
Which versions are affected by CVE-2026-43513?
19 open source packages ship an affected version, including org.apache.tomcat.embed:tomcat-embed-core, tomcat and org.apache.tomcat:tomcat. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
org.apache.tomcat.embed:tomcat-embed-core Maven | All versions | 9.0.118 |
org.apache.tomcat.embed:tomcat-embed-core Maven | All versions | 9.0.118 |
org.apache.tomcat.embed:tomcat-embed-core Maven | From 10.1.0-M1 | 10.1.55 |
org.apache.tomcat.embed:tomcat-embed-core Maven | From 10.1.0-M1 | 10.1.55 |
org.apache.tomcat.embed:tomcat-embed-core Maven | From 11.0.0-M1 | 11.0.22 |
org.apache.tomcat.embed:tomcat-embed-core Maven | From 11.0.0-M1 | 11.0.22 |
13 more packages
tomcat Bitnami | From 10.0.0 | 10.1.55, 11.0.22, 9.0.118 |
org.apache.tomcat:tomcat Maven | All versions | 9.0.118 |
org.apache.tomcat:tomcat Maven | All versions | 9.0.118 |
org.apache.tomcat:tomcat Maven | From 10.1.0-M1 | 10.1.55 |
org.apache.tomcat:tomcat Maven | From 10.1.0-M1 | 10.1.55 |
org.apache.tomcat:tomcat Maven | From 11.0.0-M1 | 11.0.22 |
org.apache.tomcat:tomcat Maven | From 11.0.0-M1 | 11.0.22 |
org.apache.tomcat:tomcat-catalina Maven | All versions | 9.0.118 |
org.apache.tomcat:tomcat-catalina Maven | All versions | 9.0.118 |
org.apache.tomcat:tomcat-catalina Maven | From 10.1.0-M1 | 10.1.55 |
org.apache.tomcat:tomcat-catalina Maven | From 10.1.0-M1 | 10.1.55 |
org.apache.tomcat:tomcat-catalina Maven | From 11.0.0-M1 | 11.0.22 |
org.apache.tomcat:tomcat-catalina Maven | From 11.0.0-M1 | 11.0.22 |
Linux distribution packages (20)
tomcat10 Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-admin-webapps Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-common Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-docs-webapp Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-el-5.0-api Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-jsp-3.1-api Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-lib Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-servlet-6.0-api Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-user-instance Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat10-webapps Red Hat:hummingbird:1 | All versions | 0:10.1.57-3.1.hum1 |
tomcat11 Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-admin-webapps Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-common Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-docs-webapp Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-el-6.0-api Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-jsp-4.0-api Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-lib Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-servlet-6.1-api Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-user-instance Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
tomcat11-webapps Red Hat:hummingbird:1 | All versions | 0:11.0.24-0.2.hum1 |
Products include Apache Tomcat.
How do I fix CVE-2026-43513?
Upgrade org.apache.tomcat.embed:tomcat-embed-core to a fixed version for your release line: 9.0.118, 10.1.55 or 11.0.22.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-43513 being exploited?
There is no known exploitation of CVE-2026-43513 in the wild and no public exploit code.
Other vulnerabilities in Apache Tomcat
Sources
Also known as BIT-tomcat-2026-43513, CLEANSTART-2026-MU35489, CLEANSTART-2026-VA89845, DEBIAN-CVE-2026-43513, GHSA-5mp6-jrq3-r938, MINI-wwr9-2xmf-9g4w and 4 more.