CVE-2026-0976 Red Hat CVE debrief

Who should care

Operators and administrators of Keycloak instances should be aware of this vulnerability and take necessary actions to verify and secure their configurations. This includes reviewing proxy settings, testing input validation, and ensuring that security mechanisms are in place to detect and prevent potential attacks. Additionally, security teams and vulnerability management teams should be aware of the potential for attackers to craft requests that could mask path segments, potentially exposing administrative or sensitive endpoints.

Technical summary

The CVE-2026-0976 vulnerability in Keycloak is due to improper input validation, specifically with RFC-compliant matrix parameters in URL path segments. This flaw may allow remote attackers to craft requests that could bypass proxy-level path filtering, potentially exposing administrative or sensitive endpoints. The vulnerability occurs because Keycloak accepts RFC-compliant matrix parameters in URL path segments, while common reverse proxy configurations may ignore or mishandle them. Operators should verify Keycloak configurations and proxy settings to ensure proper path filtering and input validation, focusing on validating matrix parameters in URL path segments.

Defensive priority

Operators should verify Keycloak configurations and proxy settings to ensure proper path filtering and input validation.

Recommended defensive actions

• Verify Keycloak configurations for proper input validation and path filtering.
• Review proxy settings to ensure correct handling of RFC-compliant matrix parameters.
• Monitor for suspicious requests that may attempt to mask path segments.
• Perform a thorough review of Keycloak instances to identify potential vulnerabilities.
• Implement additional security measures to detect and prevent potential attacks.
• Conduct regular security audits to ensure compliance with security best practices.
• Develop and implement a plan to address potential vulnerabilities in Keycloak instances.

Evidence notes

The CVE record indicates a flaw in Keycloak due to improper input validation, allowing potential bypassing of proxy-level path filtering. Evidence is based on official CVE and NVD records. Operators should verify Keycloak configurations and proxy settings to ensure proper path filtering and input validation, focusing on validating matrix parameters in URL path segments. This may involve reviewing proxy configurations, testing input validation, and ensuring that security mechanisms are in place to detect and prevent potential attacks. Additionally, defenders should be aware of the potential for attackers to craft requests that could mask path segments, potentially exposing administrative or sensitive endpoints.

Official resources