CVE-2026-39420

OVERVIEW CVE-2026-39420 is a sandbox escape vulnerability in MaxKB, an open-source enterprise AI assistant, affecting versions 2.7.1 and below. The flaw exists in the LD_PRELOAD-based sandbox protection mechanism designed to restrict untrusted Python code execution via the Tool Debug API. An authenticated attacker with tool execution privileges can exploit this vulnerability by leveraging the /usr/bin/env utility to clear environment variables and disable sandbox hooks, resulting in unrestricted remote code execution and network access. The vulnerability has been patched in version 2.8.0. SEVERITY This vulnerability carries a CVSS 3.1 score of 7.4 (HIGH) with a network-based attack vector requiring low complexity and low privileges. The attack requires prior authentication and produces cross-scope impact, enabling an attacker to achieve confidentiality, integrity, and availability breaches. The EPSS score of 0.00126 indicates relatively low probability of exploitation compared to the broader CVE landscape. EXPLOITATION STATUS There is no evidence of active exploitation in the wild, as this vulnerability is not present on the Known Exploited Vulnerabilities Catalog and shows no community activity on the Hot List. While exploit code is theoretically straightforward given the sandbox escape technique, no public proof-of-concept or exploitation reports have been documented. Organizations running MaxKB versions 2.7.1 or earlier should prioritize upgrading to version 2.8.0 to mitigate this risk.