# CVE-2026-0976: Org.keycloak/keycloak-quarkus-server: keycloak: proxy bypass due to improper handling of matrix parameters in url paths

> Attackers can bypass reverse proxy path filtering by using matrix parameters, exposing sensitive administrative endpoints in Keycloak deployments.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Jan 2026
- **Updated:** 22 Oct 2026
- **Also known as:** GHSA-v897-pv23-r8cw, MINI-37w7-7hpc-rh2x

## What is CVE-2026-0976?

CVE-2026-0976 is a low-severity vulnerability in Red Hat Build of Keycloak, published on 15 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-0976?

2 open source packages ship an affected version, including org.keycloak:keycloak-quarkus-server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.keycloak:keycloak-quarkus-server` | Maven | All versions to 26.2.5 | None |
| `org.keycloak:keycloak-quarkus-server` | Maven | All versions to 26.2.5 | None |

## How do I fix CVE-2026-0976?

Apply the vendor's patch.

## Is CVE-2026-0976 being exploited?

There is no known exploitation of CVE-2026-0976 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-0976 and fix it if it is affected.

What it is: CVE-2026-0976 is a low-severity vulnerability in Red Hat Build of Keycloak, published on 15 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-0976 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.keycloak:keycloak-quarkus-server (Maven): affected all versions up to 26.2.5; no fix listed
- org.keycloak:keycloak-quarkus-server (Maven): affected all versions up to 26.2.5; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-0976/ (Markdown: https://insights.sbomify.com/CVE-2026-0976/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-0976
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-0976
- OSV: https://osv.dev/vulnerability/CVE-2026-0976

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-0976/
Summaries are generated and may contain mistakes; the official description above is the record.