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Fencer Vulns
high 8.1

CVE-2026-4636 json

Keycloak: keycloak: uma policy bypass allows authenticated users to gain unauthorized access to victim-owned resources.

published 2026-04-02 7 mo ago modified 2026-10-26 13 d ago also BIT-keycloak-2026-4636 , EUVD-2026-18213 , GHSA-f2hx-5fx3-hmcv

cvss
8.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

A flaw was found in Keycloak. An authenticated user with the uma_protection role can bypass User-Managed Access (UMA) policy validation. This allows the attacker to include resource identifiers owned by other users in a policy creation request, even if the URL path specifies an attacker-owned resource. Consequently, the attacker gains unauthorized permissions to victim-owned resources, enabling them to obtain a Requesting Party Token (RPT) and access sensitive information or perform unauthorized actions.

Patch / fix

  • maven org.keycloak:keycloak-services 26.5.7
  • bitnami keycloak 26.2.1, 26.3.0, 26.4.1, 26.5.0
  • Red Hat Red Hat build of Keycloak 26.2 26.2-18, 26.2.15-1
  • Red Hat Red Hat build of Keycloak 26.4 26.4-14, 26.4.11-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-4636 updated cvss 8.1

keycloak: Keycloak: UMA policy bypass allows authenticated users to gain unauthorized access to victim-owned resources.

  • Red Hat build of Keycloak 26.2 rhbk/keycloak-rhel9 26.2-18, rhbk/keycloak-rhel9-operator 26.2-18, rhbk/keycloak-operator-bundle 26.2.15-1
    fixed: vendor fix RHSA-2026:6476
  • Red Hat build of Keycloak 26.2.15
    fixed: vendor fix RHSA-2026:6475
  • Red Hat build of Keycloak 26.4 rhbk/keycloak-rhel9 26.4-14, rhbk/keycloak-rhel9-operator 26.4-14, rhbk/keycloak-operator-bundle 26.4.11-1
    fixed: vendor fix RHSA-2026:6478
  • Red Hat build of Keycloak 26.4.11
    fixed: vendor fix RHSA-2026:6477

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
7 mo ago

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=2450251 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CISA ADP 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
GitHub 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
OSV 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
maven org.keycloak:keycloak-services
<26.5.7
26.5.7
bitnami keycloak
>=26.2.0, <26.2.1
>=26.2.15, <26.3.0
>=26.4.0, <26.4.1
>=26.4.11, <26.5.0
26.2.1
26.3.0
26.4.1
26.5.0

Affected products

  • Red Hat Red Hat build of Keycloak 26.2
  • Red Hat Red Hat build of Keycloak 26.2.15
  • Red Hat Red Hat build of Keycloak 26.4
  • Red Hat Red Hat build of Keycloak 26.4.11

Classification

Weakness
  • CWE-551 Incorrect Behavior Order: Authorization Before Parsing and Canonicalization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.