Craft CMS versions 5.10.0 through 5.10.12 contain an incomplete fix for CVE-2026-55794: the Controller::getPostedRedirectUrl() -> View::renderObjectTemplate() sink remained unsandboxed, and the same fix commit added a self-signing oracle in Cp::elementLabelHtml(). Because Craft/Yii HMAC tokens are not bound to a parameter name, an authenticated low-privilege control panel user with edit rights on a single element type can mint a token over attacker-controlled Twig for the returnUrl parameter and replay it as the redirect POST parameter, reaching the unsandboxed sink and achieving server-side template injection that executes arbitrary PHP code (full server compromise). The issue is fixed in 5.10.13.
https://github.com/craftcms/cms/security/advisories/GHSA-5jmw-g85v-7jv2
Published: 2026-09-16
Updated: 2026-09-22
Base Score: 9
Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:C/A:C
Severity: High
Base Score: 8.8
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity: High
Base Score: 8.7
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Severity: High
EPSS: 0.00415