CVE-2026-18203

MEDIUM
MEDIUM Priority: 0.03 BB Relevance: 63/100
Published: 2026-07-31 Modified: 2026-11-06 First seen: 2026-11-06 Status: active

Attack Surface

Network Low Complexity No Interaction Integ. Impact

CVSS Vector Breakdown

AV: Network
AC: Low
PR: Low
UI: None
S: Unchanged
C: None
I: High
A: None

Description

A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to a different group with a similar starting name to bypass security checks and gain unauthorized access to administrative functions or protected resources.

Weakness Classification (1)

Affected Software (1)

VendorProductVersion
redhat build_of_keycloak -

References & Advisories (4)

https://access.redhat.com/errata/RHSA-2026:95761
vendor-advisory x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:95762
vendor-advisory x_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2508291
issue-tracking x_refsource_REDHAT

Bug Bounty Relevance

63 / 100
✓ Network accessible
✓ Low complexity
✓ No user interaction

CVSS Score

6.5 / 10.0 v3.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

EPSS — Exploitation Probability

0.39%
Raw Score 0.003900
Percentile 33.6%
Date 2026-11-13

EPSS Trend

2026-11-13
0.00390
2026-11-12
0.00390
2026-11-10
0.00390
2026-11-09
0.00390
2026-11-08
0.00390
2026-11-07
0.00390
2026-11-06
0.00312
2026-11-05
0.00312

Intelligence Sources

mitre ref →
nvd ref →