CVE-2026-0976 — keycloak-quarkus-server
LOWCVE-2026-0976 is a low-severity (CVSS 3.7) Improper Input Validation vulnerability in org.keycloak:keycloak-quarkus-server. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.
Keycloak has an improper input validation vulnerability
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-0976.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
org.keycloak:keycloak-quarkus-serverReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
A flaw was found in Keycloak. This improper input validation vulnerability occurs because Keycloak accepts RFC-compliant matrix parameters in URL path segments, while common reverse proxy configurations may ignore or mishandle them. A remote attacker can craft requests to mask path segments, potentially bypassing proxy-level path filtering. This could expose administrative or sensitive endpoints that operators believe are not externally reachable.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.keycloak:keycloak-quarkus-server | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.keycloak:keycloak-quarkus-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of org.keycloak:keycloak-quarkus-server for CVE-2026-0976. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is rated Low for Red Hat Keycloak. The flaw arises from Keycloak's acceptance of RFC-compliant matrix parameters in URL paths, which can be mishandled by certain reverse proxy configurations. This may allow an unauthenticated attacker to bypass proxy-level path filtering and potentially expose…
To mitigate this issue, ensure that all administrative and sensitive endpoints within Keycloak are adequately protected by robust authentication and authorization policies, independent of any reverse proxy path filtering. Operators should review Keycloak's internal access controls to confirm that access to these endpoints is restricted to authorized users and roles.Source: Red Hat security advisory for CVE-2026-0976 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-0976 in your dependencies?
Find it across Maven, including transitive dependencies.