CVE-2026-43513
Description
In Apache Tomcat, LockOutRealm mishandled case sensitivity in usernames, resulting in less effective blocking of brute force attacks.
Statement
A flaw was found in Apache Tomcat's LockOutRealm. When configured with an underlying Realm where usernames are case-insensitive, the LockOutRealm does not account for case differences, potentially reducing the effectiveness of brute-force protection. Exploitation requires LockOutRealm to be configured with a case-insensitive authentication backend, which is a non-default configuration.
Mitigation
This vulnerability only affects Tomcat deployments using the LockOutRealm with a case-insensitive authentication backend. Deployments not using LockOutRealm or using case-sensitive authentication backends are not affected.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
