CVE-2026-43513: Apache Tomcat LockOutRealm Treats User Names As Vulnerability

HIGH
Advisory Identifier: GHSA-5mp6-jrq3-r938
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CVSS 7.5
CWE-178
Published
Advisory Summary

CVE-2026-43513 is a HIGH (CVSS 7.5) lockoutrealm treats user names as vulnerability (CWE-178: Improper Handling of Case Sensitivity) affecting Apache Tomcat libraries in the Maven ecosystem. The issue involves lockoutrealm treats user names as case-sensitive. Remediation is available by upgrading affected packages to version 9.0.118, 10.1.55, 11.0.22.

CVE-2026-43513 at a Glance

CVE Identifier CVE-2026-43513
GHSA Identifier GHSA-5mp6-jrq3-r938
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-178: Improper Handling of Case Sensitivity
Affected Product Apache Tomcat
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-43513

To remediate this vulnerability, upgrade all affected Apache Tomcat dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.apache.tomcat.embed:tomcat-embed-core fixed: 9.0.118 
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-core</artifactId>
    <version>9.0.118</version>
</dependency>
org.apache.tomcat.embed:tomcat-embed-core fixed: 10.1.55 
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-core</artifactId>
    <version>10.1.55</version>
</dependency>
org.apache.tomcat.embed:tomcat-embed-core fixed: 11.0.22 
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-core</artifactId>
    <version>11.0.22</version>
</dependency>
org.apache.tomcat:tomcat fixed: 9.0.118 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat</artifactId>
    <version>9.0.118</version>
</dependency>
org.apache.tomcat:tomcat fixed: 10.1.55 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat</artifactId>
    <version>10.1.55</version>
</dependency>
org.apache.tomcat:tomcat fixed: 11.0.22 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat</artifactId>
    <version>11.0.22</version>
</dependency>
org.apache.tomcat:tomcat-catalina fixed: 9.0.118 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-catalina</artifactId>
    <version>9.0.118</version>
</dependency>
org.apache.tomcat:tomcat-catalina fixed: 10.1.55 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-catalina</artifactId>
    <version>10.1.55</version>
</dependency>
org.apache.tomcat:tomcat-catalina fixed: 11.0.22 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-catalina</artifactId>
    <version>11.0.22</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.apache.tomcat.embed

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-43513, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.apache.tomcat.embed

Analyze the terminal output to locate any version of Apache Tomcat in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 9.0.118), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.apache.tomcat.embed command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-178: Improper Handling of Case Sensitivity, where the product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results. In Apache Tomcat, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2026-43513 Affected Apache Tomcat Versions

9 component(s)
Fixed Versions:
9.0.11810.1.5511.0.22
Product / Package Ecosystem Affected Versions Fixed Version
org.apache.tomcat.embed:tomcat-embed-core
maven/org.apache.tomcat.embed/tomcat-embed-core
Maven
< 9.0.118
9.0.118
org.apache.tomcat.embed:tomcat-embed-core
maven/org.apache.tomcat.embed/tomcat-embed-core
Maven
≥ 10.1.0-M1
< 10.1.55
10.1.55
org.apache.tomcat.embed:tomcat-embed-core
maven/org.apache.tomcat.embed/tomcat-embed-core
Maven
≥ 11.0.0-M1
< 11.0.22
11.0.22
org.apache.tomcat:tomcat
maven/org.apache.tomcat/tomcat
Maven
< 9.0.118
9.0.118
org.apache.tomcat:tomcat
maven/org.apache.tomcat/tomcat
Maven
≥ 10.1.0-M1
< 10.1.55
10.1.55
org.apache.tomcat:tomcat
maven/org.apache.tomcat/tomcat
Maven
≥ 11.0.0-M1
< 11.0.22
11.0.22
org.apache.tomcat:tomcat-catalina
maven/org.apache.tomcat/tomcat-catalina
Maven
< 9.0.118
9.0.118
org.apache.tomcat:tomcat-catalina
maven/org.apache.tomcat/tomcat-catalina
Maven
≥ 10.1.0-M1
< 10.1.55
10.1.55
org.apache.tomcat:tomcat-catalina
maven/org.apache.tomcat/tomcat-catalina
Maven
≥ 11.0.0-M1
< 11.0.22
11.0.22

References

NVD — CVE-2026-43513 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-43513
Security Fix Commit FIX COMMIT
https://github.com/apache/tomcat/commit/4a90d3fa93988c447cd5bb7482f76ff70d7f15c2
Security Fix Commit FIX COMMIT
https://github.com/apache/tomcat/commit/6dd75beb55bd42fc5f78e929596b25018cd17717
Security Fix Commit FIX COMMIT
https://github.com/apache/tomcat/commit/83f3e51df7b87f5f6e626951c575ded1a512e8ef
Apache Tomcat Source Repository REPOSITORY
https://github.com/apache/tomcat
lists.apache.org/thread/ytjcgldshj73... WEB
https://lists.apache.org/thread/ytjcgldshj73lcnd1sh95od5hrghwogp
Apache Tomcat Security Information SECURITY
https://tomcat.apache.org/security-10.html
Apache Tomcat Security Information SECURITY
https://tomcat.apache.org/security-11.html
Apache Tomcat Security Information SECURITY
https://tomcat.apache.org/security-9.html
Apache Tomcat Security Information SECURITY
http://www.openwall.com/lists/oss-security/2026/05/12/9

Frequently Asked Questions

What is CVE-2026-43513?
CVE-2026-43513 is a security vulnerability in Apache Tomcat involving LockOutRealm treats user names as case-sensitive under CWE-178: Improper Handling of Case Sensitivity.
Which Apache Tomcat versions are affected?
Affected versions include releases prior to 9.0.118, 10.1.55, 11.0.22 across affected packages: org.apache.tomcat.embed:tomcat-embed-core, org.apache.tomcat:tomcat, org.apache.tomcat:tomcat-catalina.
What version fixes CVE-2026-43513?
Upgrading to 9.0.118, 10.1.55, 11.0.22 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tomcat-embed-core affected?
Yes, org.apache.tomcat.embed:tomcat-embed-core is affected in releases prior to 9.0.118, 10.1.55, 11.0.22. Upgrade your dependency to 9.0.118, 10.1.55, 11.0.22 or later.
Is tomcat affected?
Yes, org.apache.tomcat:tomcat is affected in releases prior to 9.0.118, 10.1.55, 11.0.22. Upgrade your dependency to 9.0.118, 10.1.55, 11.0.22 or later.
What is the CVSS score of CVE-2026-43513?
CVE-2026-43513 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-43513?
CVE-2026-43513 is classified under CWE-178: Improper Handling of Case Sensitivity (The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.).
How can I check Maven dependencies for CVE-2026-43513?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.apache.tomcat.embed'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5mp6-jrq3-r938",
  "modified" : "2026-05-18T20:31:54Z",
  "published" : "2026-05-12T18:30:38Z",
  "aliases" : [ "CVE-2026-43513" ],
  "summary" : "Apache Tomcat: LockOutRealm treats user names as case-sensitive",
  "details" : "Improper Handling of Case Sensitivity vulnerability in LockOutRealm in Apache Tomcat.\n\nThis 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.\nOlder unsupported versions may also be affected.\n\nUsers are recommended to upgrade to version 11.0.22, 10.1.55 or 9.0.118 which fix the issue.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
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    },
    "ranges" : [ {
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      } ]
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    },
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  }, {
    "package" : {
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    },
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  }, {
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    },
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      }, {
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      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-43513"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/apache/tomcat/commit/4a90d3fa93988c447cd5bb7482f76ff70d7f15c2"
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  }, {
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  }, {
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  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2026/05/12/9"
  } ],
  "database_specific" : {
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    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-18T20:31:54Z",
    "nvd_published_at" : "2026-05-12T16:16:18Z"
  }
}