Sandboxie-Plus CVE-2026-45313

Exploitation requires the attacker to first be running code inside a Sandboxie-Plus sandbox (a sandboxed process) so they can issue a GUI_WND_HOOK_REGISTER request to the local SYSTEM GuiServer - this is a local sandbox-escape, not a remote attack. The specific trigger is the window-hook registration/notification path: the attacker supplies unvalidated hthread and hproc fields that GuiServer later passes to OpenThread and QueueUserAPC. Limiting factors from the CVSS vector are AC:H (high complexity - the WndHookNotifySlave path must be reached and a valid thread targeted, implying timing or a triggering hook event) and UI:R (user interaction required, so a triggering GUI/hook condition or user action is needed rather than fully autonomous exploitation). It only affects Sandboxie-Plus versions before 1.17.6 on Windows; hosts on 1.17.6/5.72.6 or later are not exploitable.

The supplied CVSS 3.1 base score is 7.7 (High) with vector AV:L/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H - local vector, high attack complexity, scope change, and full confidentiality/integrity/availability impact, which correctly captures a boundary-crossing escape. There is no EPSS score, no KEV listing, and no POC referenced in the provided intelligence, so probabilistic and in-the-wild signals are all absent; risk is driven by impact severity rather than by evidence of exploitation. The AC:H and UI:R metrics imply the attack is not trivially automatable and may depend on timing or a triggering GUI-hook event, which tempers urgency relative to a wormable network flaw. The most important caveat is exposure prerequisite: the vector is AV:L and the attacker must already be executing code inside a sandbox, so this is a serious defense-in-depth failure (isolation bypass + local privilege escalation to SYSTEM) rather than a remote entry point. Note also a modeling tension - PR:N is used even though the attacker needs an existing foothold within a sandboxed process; treat 'no privileges' as 'no host privileges,' not 'no code execution at all.'

An attacker who has already achieved code execution inside a Sandboxie box - for example by luring a user to open malicious content in a sandboxed browser - sends a crafted GUI_WND_HOOK_REGISTER request to the SYSTEM GuiServer with an hthread handle and an hproc function pointer under their control. When the hook fires, GuiServer executes the attacker's pointer via QueueUserAPC as SYSTEM in a host process, breaking out of the sandbox and elevating to full system compromise. No public POC is referenced, and the CVSS AC:H/UI:R metrics indicate the attacker likely must satisfy specific timing or hook-triggering conditions rather than firing a single deterministic request.