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Fencer Intel
low 3.7

CVE-2026-0976 json

Org.keycloak/keycloak-quarkus-server: keycloak: proxy bypass due to improper handling of matrix parameters in url paths

published 9mo ago modified 18d ago also EUVD-2026-2822 , GHSA-v897-pv23-r8cw

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

A flaw was found in Keycloak. This improper input validation vulnerability occurs because Keycloak accepts RFC-compliant matrix parameters in URL path segments, while common reverse proxy configurations may ignore or mishandle them. A remote attacker can craft requests to mask path segments, potentially bypassing proxy-level path filtering. This could expose administrative or sensitive endpoints that operators believe are not externally reachable.

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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-2026-0976 updated cvss 3.7

org.keycloak/keycloak-quarkus-server: Keycloak: Proxy bypass due to improper handling of matrix parameters in URL paths

  • Red Hat Build of Keycloak keycloak-quarkus-server
    affected: workaround, no fix available
  • Red Hat JBoss Enterprise Application Platform 8 keycloak-quarkus-server, keycloak-quarkus-server-app, keycloak-quarkus-server-deployment Red Hat JBoss Enterprise Application Platform Expansion Pack keycloak-quarkus-server, keycloak-quarkus-server-app, keycloak-quarkus-server-deployment
    affected: workaround, no fix available “Fix deferred”
  • Red Hat build of Keycloak 26.4.9
    fixed: vendor fix RHSA-2026:2365

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
partial
Assessed
9mo ago

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
GitHub 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
maven org.keycloak:keycloak-quarkus-server
<=26.2.5
 no fix listed

Affected products

  • Red Hat Red Hat build of Keycloak 26.4.9
  • Red Hat Red Hat Build of Keycloak
  • Red Hat Red Hat JBoss Enterprise Application Platform 8
  • Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Intel 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.