CVE-2026-18209
Low
No strong exploitation signal.
CVSS base
3.4
LOW
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N
EPSS — probability of exploitation (30 days)
0.2%
14.3th percentile
CISA KEV
Not listed
Weakness / dates
CWE-1288
Published 2026-07-31 · modified 2026-09-16
CVSS breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N
| Attack Vector | N | Network |
| Attack Complexity | H | High |
| Privileges Required | N | None |
| User Interaction | R | Required |
| Scope | C | Changed |
| Confidentiality | N | None |
| Integrity | L | Low |
| Availability | N | None |
Timeline
- 2026-07-31 — Published (NVD)
- 2026-09-16 — Last modified (NVD)
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.