# CVE-2026-18217: Auth bypass in Red Hat Build of Keycloak

> Attackers can hijack user sessions by exploiting parameter pollution in SAML HTTP-Redirect responses when wildcard redirect URLs are configured.

- **Severity:** Low 3.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 31 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** GHSA-82v3-6227-jc8x

## What is CVE-2026-18217?

CVE-2026-18217 is a low-severity authentication bypass vulnerability in Redhat Build of Keycloak, published on 31 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A flaw was found in the SAML protocol implementation of Keycloak, an open-source identity and access management solution. The issue occurs when Keycloak handles SAML authentication requests using the HTTP-Redirect binding. If a client is configured with a wildcard redirect URL, an attacker can craft a request that includes malicious parameters. When a user authenticates, Keycloak appends its legitimate response to the attacker's parameters. This can cause some service providers to process the attacker's data instead of the real login information, potentially leading to a user being logged into the wrong account.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-18217?

It affects 1 product.


Products: Redhat Build of Keycloak.

## How do I fix CVE-2026-18217?

No fix has been published for CVE-2026-18217 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-18217 being exploited?

There is no known exploitation of CVE-2026-18217 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Build of Keycloak

- [CVE-2026-15572](https://insights.sbomify.com/CVE-2026-15572/): Keycloak-services: keycloak-services: dcr protocol mapper type-swap policy bypass allows privilege escalation (high 8.8)
- [CVE-2026-3047](https://insights.sbomify.com/CVE-2026-3047/): Keycloak SAML Broken has Authentication Bypass by Primary Weakness (high 8.8)
- [CVE-2026-15573](https://insights.sbomify.com/CVE-2026-15573/): Keycloak-services: keycloak-services: authorization bypass via unnormalized uri matching in pathmatcher (high 8.1)
- [CVE-2026-16102](https://insights.sbomify.com/CVE-2026-16102/): Keycloak-services: keycloak-services: default dcr policy allows role forgery via user property mappers (high 8.1)
- [CVE-2026-1609](https://insights.sbomify.com/CVE-2026-1609/): Org.keycloak/keycloak-quarkus-server: keycloak: unauthorized access via jwt authorization grant with disabled users (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18217 and fix it if it is affected.

What it is: CVE-2026-18217 is a low-severity authentication bypass vulnerability in Redhat Build of Keycloak, published on 31 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-18217 in the wild and no public exploit code.

Affected product: Redhat Build of Keycloak. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-18217/ (Markdown: https://insights.sbomify.com/CVE-2026-18217/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18217
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18217
- OSV: https://osv.dev/vulnerability/CVE-2026-18217

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18217/
Summaries are generated and may contain mistakes; the official description above is the record.