CVE-2026-18209

mediumpriority · track · 19EPSS 0.004 · 35 %ileDEEUUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
0.41% (35th) EPSS
CVSS 4.7 · medium
Is it mine?
3 products
Check your exposure
Who says so?
5 sources
cnnvd · enisa_euvd · cert_bund · nvd

EPSS · scored 2026-10-27

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

4.7
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · low–medium · 3.4–4.7

v3.14.7mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:Nprimary · NVD / NIST USexploitability 2.8 · impact 1.4
v3.13.4lowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:Nsecondary · ENISA EU
v3.13.4lowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:Nsecondary · secalert@redhat.com USexploitability 1.6 · impact 1.4
v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N/E:Usecondary · CVSS-BT (t0sche)
02

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Trackcoordinatorcisa_ssvcUS
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-1288US
04

affected products (3)

Products and version ranges known to be affected.

05

advisories (2)

Vendor and ecosystem advisories describing this.

  • WID-SEC-W-2026-2614Keycloak: Mehrere SchwachstellenDeutsch2026-08-02csaf · cert_bundDE

    Ein Angreifer kann mehrere Schwachstellen in Keycloak ausnutzen, um seine Privilegien zu erhöhen, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren und sensible Informationen offenzulegen.

  • BIT-keycloak-2026-18209Keycloak-services: keycloak-services: oidc redirect_uri fragment bypass in http parameter pollution check2026-08-31vendor · osvUS

    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.

06

also known as (3)

Other names and identifiers for this entity.

07

sources

Which sources assert this record, and when.

cnnvdenisa_euvdcert_bundnvdosvNVDCVE.orgMITRE
published 2026-07-31modified 2026-09-16
08

references (8)

External citations — patches, advisories, analysis.

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