CVE-2026-39420

MaxKB is an open-source AI assistant for enterprise. In versions 2.7.1 and below, an incomplete sandbox protection mechanism allows an authenticated user with tool execution privileges to escape the LD_PRELOAD-based sandbox. By env command the attacker can clear the environment variables and drop the sandbox.so hook, leading to unrestricted Remote Code Execution (RCE) and network access. MaxKB restricts untrusted Python code execution via the Tool Debug API by injecting sandbox.so through the LD_PRELOAD environment variable. This intercepts sensitive C library functions (like execve, socket, open) to restrict network and file access. However, a patch allowed the /usr/bin/env utility to be executed by the sandboxed user. When an attacker is permitted to create subprocesses, they can execute the env -i python command. The -i flag instructs env to completely clear all environment variables before running the target program. This effectively drops the LD_PRELOAD environment variable. The newly spawned Python process will therefore execute natively without any sandbox hooks, bypassing all network and file system restrictions. This issue has been fixed in version 2.8.0.

The following products are affected by CVE-2026-39420 vulnerability.

Here, you will find a curated list of external links that provide in-depth information to CVE-2026-39420.

URL	Resource
https://github.com/1Panel-dev/MaxKB/commit/2d17b08e6b060329803754a05e806d0ddecf3fa8
https://github.com/1Panel-dev/MaxKB/releases/tag/v2.8.0
https://github.com/1Panel-dev/MaxKB/security/advisories/GHSA-7wgv-v2r3-7f7w