Sandboxie-Plus CVE-2026-34458

Attacker must have local access to the Windows system with at least standard user (non-admin) credentials. Sandboxie-Plus version 1.17.2 or earlier must be installed with the background service (SbieSvc.exe) running, which is the default installation mode. No special product features, non-default configurations, or specific sandbox policies need to be enabled-the vulnerable IPC message handlers are always active in affected versions. Exploitation does NOT require user interaction, admin privileges, or network access. The only limiting factor is local authentication: remote attackers cannot exploit this vulnerability without first compromising a local user account through separate means.

CVSS 9.3 indicates Critical severity with local vector, low complexity, low privileges required, and high impact across confidentiality, integrity, availability, and scope (AV:L/AC:L/PR:L/SC:H/SI:H/SA:H). Real-world risk is high for multi-user Windows systems running Sandboxie-Plus 1.17.2 or earlier: any standard user can achieve SYSTEM escalation without requiring admin interaction or non-default configurations. However, this is NOT a remote threat-attacker must already have local access with at least standard user credentials. No EPSS score provided in input data. Not listed in CISA KEV, suggesting no confirmed widespread exploitation, but the GitHub security advisory (GHSA-6xqg-2cjq-95qf) provides sufficient technical detail for any skilled attacker to reproduce the CRLF injection technique. Primary risk is in enterprise environments with shared workstations, terminal servers, or multi-tenant Windows hosts where Sandboxie-Plus is deployed for application isolation but untrusted local users exist. Single-user workstations face lower risk unless compromised by malware already running with user-level access seeking escalation.

A standard local user on a corporate workstation with Sandboxie-Plus 1.17.2 sends a crafted IPC message to the SYSTEM-level SbieSvc service using MSGID_SBIE_INI_SET_SETTING, targeting a section beginning with UserSettings_ to bypass authorization. The attacker injects CRLF sequences in the setting name parameter to break out of UserSettings_ and create a new sandbox section header [MaliciousSandbox] with directives like Enabled=y, DropAdminRights=N, and OpenWinClass=*, then launches a process in this unrestricted sandbox that inherits SYSTEM privileges from the service. The attacker now has full system control without requiring UAC prompts or admin credentials.