CVE-2026-18215: Keycloak-services: keycloak-services: microsoft external access-token exchange bypasses configured tenant
Vulnerability summary
CVE-2026-18215 is a high (CVSS 8.1) Improper Authentication vulnerability in redhat build_of_keycloak. EPSS estimates a 0.40% chance of exploitation in the next 30 days, higher than 33.4% of scored vulnerabilities.
Timeline
- 31-07-2026PublishedVulnerability first disclosed.
- 16-09-2026Last modifiedVulnerability information updated.
Description
Keycloak provides a way to let users log in using Microsoft accounts while restricting access to a specific organization (tenant). A flaw was discovered where this restriction is ignored when using the token exchange feature. This means an attacker with a valid Microsoft token from a completely different organization could gain access to the Keycloak realm, potentially accessing sensitive data or performing unauthorized actions.
CVSS metrics
2 scores · 2 sources · 1 version- CVE.orgCNA6.8MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:NDiffers
EPSS trend
Probability
0.40%
Chance of exploitation in the next 30 days
Percentile
33%
Versus all other CVEs
30-day change
Increase +0.18 pp
From 0.23% on 22-09-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Redhat1 product
1 vendor · 1 product