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.
CVSS Details
- CVSS 4.0 Base Score: 8.7 (HIGH)
- CVSS 4.0 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X)
- CVSS 3.1 Base Score: 8.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
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