# CVE-2026-18217: Keycloak SAML HTTP Parameter Pollution in HTTP-Redirect binding

Source: https://junglewise.ai/threats/cve-2026-18217-keycloak-saml-http-parameter-pollution-in-http-redirect-binding  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-31. Updated: 2026-07-31  
License: CC BY 4.0 with a link back

CVE-2026-18217 · Severity: low · CVSS 3.4 · Published 2026-07-31

Keycloak, a tool used for managing user identities and logins, has a security flaw in how it handles certain login requests. If a system is configured with broad redirect rules, an attacker can trick the system into sending a user's login information to the wrong place. This could result in a user being logged into an account controlled by the attacker, potentially leading to unauthorized access or session swapping.

Technologies: [Keycloak](https://junglewise.ai/threats/technologies/keycloak), [Red Hat build of Keycloak](https://junglewise.ai/threats/technologies/red-hat-build-of-keycloak). Vendors: [Keycloak](https://junglewise.ai/threats/vendors/keycloak), [Red Hat](https://junglewise.ai/threats/vendors/red-hat).

## Quick answers

**Is CVE-2026-18217 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-18217 being exploited in the wild.

**How severe is CVE-2026-18217?** Low severity, with a CVSS score of 3.4, published 31 July 2026.

**Which products and versions are affected?** Keycloak All versions; Red Hat build of Keycloak All versions.

**Is there a fix for CVE-2026-18217?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-18217 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-18217?** Check whether you run Keycloak or Red Hat build of Keycloak at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A HTTP Parameter Pollution (HPP) vulnerability exists in the org.keycloak.protocol.saml package of Keycloak. The flaw occurs because the SAML HTTP-Redirect binding response preserves the full query string from the initial authentication request. If a client is configured with a wildcard redirect URI, an attacker can craft an AuthnRequest with an AssertionConsumerServiceURL containing pre-filled SAMLResponse and RelayState parameters. Keycloak then appends its legitimate parameters to the URL, resulting in duplicates. Service providers that prioritize the first occurrence of a query parameter may process the attacker's data instead of the legitimate response, enabling session swapping or login CSRF.

## Affected products

- Red Hat Red Hat Build of Keycloak All versions
- Keycloak Keycloak All versions

## Timeline

- 2026-07-29: disclosed: Reported via Red Hat Bugzilla
- 2026-07-31: advisory: NVD and Red Hat advisory published

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/jbossnetwork/restricted/listSoftware.html](https://access.redhat.com/jbossnetwork/restricted/listSoftware.html)
- [https://access.redhat.com/security/cve/CVE-2026-18217](https://access.redhat.com/security/cve/CVE-2026-18217)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2508311](https://bugzilla.redhat.com/show_bug.cgi?id=2508311)

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