CVE-2023-6563

Medium

Elevated severity or exploit probability.

CVSS base

7.7 HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

EPSS — probability of exploitation (30 days)

1.2%

67.9th percentile

CISA KEV

Not listed

Weakness / dates

CWE-770

Published 2023-12-14 · modified 2026-09-22

CVSS breakdown

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

Attack Vector	N	Network
Attack Complexity	L	Low
Privileges Required	L	Low
User Interaction	N	None
Scope	C	Changed
Confidentiality	N	None
Integrity	N	None
Availability	H	High

Timeline

2023-12-14 — Published (NVD)
2026-09-22 — Last modified (NVD)

Description

An unconstrained memory consumption vulnerability was discovered in Keycloak. It can be triggered in environments which have millions of offline tokens (> 500,000 users with each having at least 2 saved sessions). If an attacker creates two or more user sessions and then open the "consents" tab of the admin User Interface, the UI attempts to load a huge number of offline client sessions leading to excessive memory and CPU consumption which could potentially crash the entire system.

Affected

redhat

References

Official: NVD · CVE.org