Keycloak vulnerable to Improper Client Certificate Validation for OAuth/OpenID clients

Description

When a Keycloak server is configured to support mTLS authentication for OAuth/OpenID clients, it does not properly verify the client certificate chain. A client that possesses a proper certificate can authorize itself as any other client and therefore access data that belongs to other clients.

Basic information

Type
reviewed
Severity
high
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2023-06-30 20:31:37 UTC
Updated
2023-11-08 05:01:45 UTC
GitHub reviewed
2023-06-30 20:31:37 UTC
NVD published
2023-10-04

EPSS Score

Score Percentile
0.32% 55.34%

CVSS Scores

Base score Version Severity Vector
7.1 3.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/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:L)
A normal user session is enough; they don’t have to be admin.
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: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-295 Improper Certificate Validation

Credits

  • artsploit (analyst)

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 < 21.1.2 21.1.2

References

cvelogic Threat Intelligence