Improper Handling of Case Sensitivity in Apache Tomcat - CVE-2026-43513

Vulnerability identifier: #VU131179

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-43513

CWE-ID: CWE-178

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to weaken brute-force protection against a user's password.

The vulnerability exists due to improper input handling in LockOutRealm when processing case-insensitive user names. A remote attacker can vary the case of a user name during authentication attempts to weaken brute-force protection against a user's password.

This affects Realms where user names are treated as case insensitive.

Apache Tomcat
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 15 SP4
Debian Linux
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
Red Hat Enterprise Linux Server - TUS
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Ubuntu
Web and Scripting Module
openSUSE Leap
openEuler
Db2 Developer Extension
Storage Defender Copy Data Management
Maximo Application Suite Ai Service
CICS Transaction Gateway Desktop Edition
CICS Transaction Gateway for Multiplatforms
ApplinX
Dell Wyse Management Suite
IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data
IBM Watson Discovery for IBM Cloud Pak for Data
Jira Service Management Data Center
Crowd Data Center
Confluence Data Center
Jira Software Data Center
Bamboo Data Center
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
tomcat6 (Ubuntu package)
tomcat10 (Ubuntu package)
tomcat-help
tomcat-jsvc
tomcat
tomcat-javadoc
tomcat-servlet-4_0-api
tomcat-admin-webapps
tomcat-lib
tomcat-jsp-2_3-api
tomcat-el-3_0-api
tomcat-docs-webapp
tomcat-webapps
tomcat (Red Hat package)
tomcat9 (Red Hat package)
tomcat10 (Debian package)
tomcat10-servlet-6_0-api
tomcat10-lib
tomcat10-admin-webapps
tomcat10
tomcat10-webapps
tomcat10-el-5_0-api
tomcat10-jsp-3_1-api
tomcat11 (Debian package)
tomcat11-el-6_0-api
tomcat11-admin-webapps
tomcat11
tomcat11-servlet-6_1-api
tomcat11-doc
tomcat11-jsvc
tomcat11-docs-webapp
tomcat11-webapps
tomcat11-lib
tomcat11-jsp-4_0-api
tomcat11-embed

Install security update from vendor's website.

Apache Tomcat - addressed in versions 9.0.118, 10.1.55, 11.0.22
Db2 Developer Extension - update to 1.1.2
Storage Defender Copy Data Management - update to 2.3.1.0
IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data - update to 5.4.0 Patch 3
IBM Watson Discovery for IBM Cloud Pak for Data - update to 5.3.2
Jira Service Management Data Center - addressed in versions 10.3.22, 11.3.7
Crowd Data Center - update to 7.2.2
Confluence Data Center - addressed in versions 9.2.21, 10.2.13
Maximo Application Suite Ai Service - update to 9.1.16
Jira Software Data Center - addressed in versions 9.12.36, 10.3.22, 11.3.7
Bamboo Data Center - addressed in versions 10.2.20, 12.1.8
tomcat6 (Ubuntu package) - addressed in versions 6.0.39-1ubuntu0.1+esm3, 7.0.52-1ubuntu0.16+esm2, 7.0.68-1ubuntu0.4+esm4
tomcat10 (Ubuntu package) - addressed in versions 9.0.16-3ubuntu0.18.04.2+esm8, 9.0.31-1ubuntu0.9+esm3, 9.0.58-1ubuntu0.2+esm4, 9.0.70-2ubuntu0.1+esm3, 9.0.95-1ubuntu1.1, 9.0.115-1ubuntu0.1, 10.1.16-1ubuntu0.1~esm4, 10.1.40-1ubuntu1.25.10.1, 10.1.40-1ubuntu1.26.04.1
tomcat-help - update to 9.0.118-1
tomcat-jsvc - update to 9.0.118-1
tomcat - update to 9.0.118-1
tomcat-javadoc - update to 9.0.118-3.166.1
tomcat-servlet-4_0-api - addressed in versions 9.0.118-3.166.1, 9.0.118-150200.108.1
tomcat-admin-webapps - addressed in versions 9.0.118-3.166.1, 9.0.118-150200.108.1
tomcat-lib - addressed in versions 9.0.118-3.166.1, 9.0.118-150200.108.1
tomcat-jsp-2_3-api - addressed in versions 9.0.118-3.166.1, 9.0.118-150200.108.1
tomcat - addressed in versions 9.0.118-3.166.1, 9.0.118-150200.108.1
tomcat-el-3_0-api - addressed in versions 9.0.118-3.166.1, 9.0.118-150200.108.1
tomcat-docs-webapp - update to 9.0.118-3.166.1
tomcat-webapps - addressed in versions 9.0.118-3.166.1, 9.0.118-150200.108.1
tomcat (Red Hat package) - addressed in versions 9.0.120-1.el8_8, 9.0.120-1.el9_2, 9.0.120-1.el9_4, 9.0.120-2.el9_8, 10.1.49-1.el10_0, 10.1.49-4.el10_2
tomcat9 (Red Hat package) - update to 9.0.120-1.el10_2
tomcat10 (Debian package) - addressed in versions 10.1.55-1~deb12u1, 10.1.55-1~deb13u1
tomcat10-servlet-6_0-api - update to 10.1.55-150200.5.67.1
tomcat10-lib - update to 10.1.55-150200.5.67.1
tomcat10-admin-webapps - update to 10.1.55-150200.5.67.1
tomcat10 - update to 10.1.55-150200.5.67.1
tomcat10-webapps - update to 10.1.55-150200.5.67.1
tomcat10-el-5_0-api - update to 10.1.55-150200.5.67.1
tomcat10-jsp-3_1-api - update to 10.1.55-150200.5.67.1
tomcat11 (Debian package) - update to 11.0.22-1~deb13u1
tomcat11-el-6_0-api - update to 11.0.22-150600.13.21.1
tomcat11-admin-webapps - update to 11.0.22-150600.13.21.1
tomcat11 - update to 11.0.22-150600.13.21.1
tomcat11-servlet-6_1-api - update to 11.0.22-150600.13.21.1
tomcat11-doc - update to 11.0.22-150600.13.21.1
tomcat11-jsvc - update to 11.0.22-150600.13.21.1
tomcat11-docs-webapp - update to 11.0.22-150600.13.21.1
tomcat11-webapps - update to 11.0.22-150600.13.21.1
tomcat11-lib - update to 11.0.22-150600.13.21.1
tomcat11-jsp-4_0-api - update to 11.0.22-150600.13.21.1
tomcat11-embed - update to 11.0.22-150600.13.21.1
Dell Wyse Management Suite - update to 2605 HF1

• https://tomcat.apache.org/security-11.html#Fixed_in_Apache_Tomcat_11.0.22
• https://github.com/apache/tomcat/commit/83f3e51df7b87f5f6e626951c575ded1a512e8ef

• Multiple vulnerabilities in Apache Tomcat
• openEuler update for tomcat
• Ubuntu update for tomcat6
• Debian update for tomcat11
• Debian update for tomcat10
• SUSE update for tomcat
• Ubuntu update for tomcat10
• SUSE update for tomcat11
• SUSE update for tomcat10
• Multiple vulnerabilities in IBM ApplinX
• Multiple vulnerabilities in IBM Watson Discovery Cartridge
• Multiple vulnerabilities in Bamboo Data Center
• Multiple vulnerabilities in Confluence Data Center
• Multiple vulnerabilities in Jira Service Management Data Center and Jira Service Management Server
• Multiple vulnerabilities in Jira Software Data Center
• Multiple vulnerabilities in IBM Storage Defender Copy Data Management
• SUSE update for tomcat
• Multiple vulnerabilities in IBM Maximo AI Service
• Multiple vulnerabilities in IBM CICS Transaction Gateway for Multiplatforms
• Multiple vulnerabilities in CICS Transaction Gateway Desktop Edition
• Multiple vulnerabilities in IBM Watson Speech Services Cartridge
• Multiple vulnerabilities in Dell Wyse Management Suite (WMS)
• Multiple vulnerabilities in Crowd Data Center
• Multiple vulnerabilities in IBM Db2 Developer Extension
• Red Hat Enterprise Linux 10 update for tomcat
• Red Hat Enterprise Linux 10 update for tomcat9
• Red Hat Enterprise Linux 9 update for tomcat
• Red Hat Enterprise Linux 9 update for tomcat
• Red Hat Enterprise Linux 9 update for tomcat
• Red Hat Enterprise Linux 8 update for tomcat
• Red Hat Enterprise Linux 10 update for tomcat