CVE-2026-18209

3.4 LOW 0.4% exploit odds Fix listed Other

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in, but needs a user to act. Limited direct impact.
Exploit odds: 0.4% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-07-31 08:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-09-16 19:17 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.4% in the next 30 days (EPSS).
Severity: 3.4 LOW (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-07-31 08:16 UTC
Last modified: 2026-09-16 19:17 UTC
Exploit probability: 0.4% · EPSS, next 30 days
Weakness: CWE-1288
Record status: Modified

Affected

Redhat Build Of Keycloak

Attack profile CVSS 3.1 · 3.4

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: Required
Scope: Changed
Confidentiality: None
Integrity: Low
Availability: None

Raw vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-18209.md and follow it. Check whether this project is affected by CVE-2026-18209. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

· More options · Status badge

Download Square Reddit

Fix and advisories

References

NVD record · CVE.org record