Keycloak: Arbitrary code execution via Stored Cross-Site Scripting (XSS) in organization selection login page

Description

A flaw was found in Keycloak, specifically in the organization selection login page. A remote attacker with manage-realm or manage-organizations administrative privileges can exploit a Stored Cross-Site Scripting (XSS) vulnerability. This flaw occurs because the organization.alias is placed into an inline JavaScript onclick handler, allowing a crafted JavaScript payload to execute in a user's browser when they view the login page. Successful exploitation enables arbitrary JavaScript execution, potentially leading to session theft, unauthorized account actions, or further attacks against users of the affected realm.

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Source code
Browse source ↗
Published (advisory)
2026-04-14 15:30:35 UTC
Updated
2026-04-16 01:34:59 UTC
GitHub reviewed
2026-04-16 01:34:56 UTC
NVD published
2026-04-14

EPSS Score

Score Percentile
0.05% 15.53%

CVSS Scores

Base score Version Severity Vector
6.9 3.1
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

CWEs

CWE id Name
CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
maven org.keycloak:keycloak-services <= 26.5.5

References

cvelogic Threat Intelligence