Insufficient Session Expiration in Umbraco CMS - #VU158823
Published: November 3, 2026
Vulnerability identifier: #VU158823
CSH Severity: Medium
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-613
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to retain unauthorized access to the Umbraco backoffice after a user signs out.
The vulnerability exists due to insufficient session expiration in the Umbraco backoffice logout functionality when processing a sign-out request. A remote attacker can reuse a previously obtained backoffice authentication cookie (UMB_UCONTEXT*) until it expires to access backoffice information and perform actions with the signed-out user's permissions.
Affected software
Umbraco CMS
Remediation
Install security update from vendor's website.
Umbraco CMS - addressed in versions 17.7.2, 18.2.2