Sandboxie-Plus CVE-2026-34596

The following specific, concrete conditions must be met for exploitation: the target system must have Sandboxie-Plus version 1.17.2 or earlier installed; the user of the target system must explicitly initiate addon installation through the SandMan user interface (the vulnerability is not triggered by automatic updates or background operations); the attacker must have local system access (local user account or code execution context on the target machine); the attacker must have write permissions to the user's %TEMP% directory, which is true by default for any local user on Windows; and the attacker must successfully win the race condition between UpdUtil's hash verification operation and install.bat's file extraction operation, which is reliably achievable within a narrow time window (typically milliseconds to seconds) using standard file-locking or monitoring APIs. The vulnerability does NOT require elevated privileges to trigger, network access, or special system configuration. The attacker must observe or predict the exact timing of the addon installation process, making the attack window bounded but reliably exploitable through automated monitoring.

The CVSS 4.0 score of 5.4 with AV:L (local), AC:L (low complexity), AT:P (predictable timing), and PR:L (low privilege requirement) accurately reflects a moderate real-world risk. The attack requires local system access and user interaction (UI:A - the user must explicitly install an addon), which limits the attack surface compared to a remote vector. However, the VC:H/VI:H/VA:H confidentiality, integrity, and availability impacts indicate full system compromise once code execution as SYSTEM is achieved. The AT:P temporal component indicates exploitability depends on successful race condition timing, which is reliably achievable using standard file-locking or monitoring techniques (e.g., watchdir utilities). The absence of KEV listing and public POC code suggests limited documented real-world exploitation, but the attack is trivial for any attacker with local access who understands race conditions. Organizations running Sandboxie-Plus should treat this as a medium-priority patch: it requires user action to trigger and local system access, but the privilege escalation path is complete and leads to full OS compromise. Threat model relevance depends on whether users can be socially engineered into installing untrusted addons or whether internal threat actors have local system access.

A local unprivileged attacker (or malware running with standard user privileges) monitors the user's Sandboxie-Plus addon installation activity, perhaps by watching the %TEMP% directory. When a user initiates addon installation through SandMan, the attacker uses a file monitoring tool or custom script to detect creation of files.cab in %TEMP%\sandboxie-updater. The attacker then executes a race-condition exploit that continuously reads the hash verification status from the install.bat process and, at the precise moment after hash verification completes but before extraction begins, atomically replaces files.cab with a malicious cabinet containing an executable (e.g., a reverse shell or credential harvester). When install.bat continues and extracts the cabinet, it executes the attacker's payload with SYSTEM privileges, granting full OS compromise without user awareness or UAC prompts.