Keycloak has an Out-of-bounds Read

Description

A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service.

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
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Repository advisory
Source code
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Published (advisory)
2026-05-28 06:31:10 UTC
Updated
2026-07-01 21:27:38 UTC
GitHub reviewed
2026-07-01 21:27:37 UTC
NVD published
2026-05-28

EPSS Score

Score Percentile
0.42% 33.52%

CVSS Scores

Base score Version Severity Vector
5.3 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L 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:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.

Identifiers

CWEs

CWE id Name
CWE-125 Out-of-bounds Read

Affected packages (2)

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

Ecosystem Package Vulnerable range First patched Vulnerable functions
maven org.keycloak:keycloak-services <= 26.4.7
maven org.keycloak:keycloak-services >= 26.5.0, < 26.6.3 26.6.3

References

cvelogic Threat Intelligence