---
cve: "CVE-2026-18209"
severity: "LOW"
cvss: 3.4
epss: "19%"
vendor: "Generic Security"
kev: false
exploited: false
published: "2026-07-31 08:16:27"
tags: [cve, security, low]
source: tsecurity.de CVE-Dossier
exported: "2026-09-04T02:49:48+02:00"
---

# CVE-2026-18209

> 3.4 LOW

## Beschreibung

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-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Erforderlich | good |
| S Scope | Verändert | bad |
| C Vertraulichkeit | Keine | good |
| I Integrität | Gering | warn |
| A Verfügbarkeit | Keine | good |

## Referenzen

- <https://access.redhat.com/security/cve/CVE-2026-18209>
- <https://bugzilla.redhat.com/show_bug.cgi?id=2508305>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-18209) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_