CVE-2026-39421: MaxKB: Sandbox escape via ctypes and unhooked SYS_pkey_mprotect

MaxKB is an open-source AI assistant for enterprise. Versions 2.7.1 and below contain a sandbox escape vulnerability in the ToolExecutor component. By leveraging Python's ctypes library to execute raw system calls, an authenticated attacker with workspace privileges can bypass the LDPRELOAD-based sandbox.so module to achieve arbitrary code execution via direct kernel system calls, enabling full network exfiltration and container compromise. The library intercepts critical standard system functions such as execve, system, connect, and open. It also intercepts mprotect to prevent PROTEXEC (executable memory) allocations within the sandboxed Python processes, but pkeymprotect is not blocked. This issue has been fixed in version 2.8.0.