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CVE-2026-18209

3.4 · LOW

A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows.

Published Jul 31, 2026CWE-1288EPSS 0.41%

Overview

CVE-2026-18209 is a low-severity vulnerability. It was published on July 31, 2026 and has a CVSS 3.1 base score of 3.4 (LOW).

This vulnerability has a CVSS 3.1 base score of 3.4, rated LOW. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows. The issue occurs because the security check designed to prevent HTTP parameter pollution only inspects the query portion of a redirect URL and ignores the fragment portion. When a client is configured with a wildcard redirect URI, an attacker can use this to inject duplicate security parameters into the login response. If a client application is not configured correctly, it might trust the attacker's injected data instead of the real security information from Keycloak, leading to session fixation or account confusion.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refaccess.redhat.com/security/cve/CVE-2026-18209Refbugzilla.redhat.com/show_bug.cgi?id=2508305

How CyberStrike helps

Frequently asked questions

What is CVE-2026-18209?

CVE-2026-18209 is a low-severity vulnerability. It was published on July 31, 2026 and has a CVSS 3.1 base score of 3.4 (LOW).

How severe is CVE-2026-18209?

This vulnerability has a CVSS 3.1 base score of 3.4, rated LOW. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-18209?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-18209?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-18209 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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