CVE-2026-18209A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows.
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 4.7 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
- Weakness (CWE)
- CWE-1288
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Sep 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
redhat build_of_keycloak redhat:build_of_keycloak | all versions | NVD |
References
- https://access.redhat.com/errata/RHSA-2026:68277
- https://access.redhat.com/errata/RHSA-2026:68278
- https://access.redhat.com/security/cve/CVE-2026-18209vendor-advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2508305issue-tracking, vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.