Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Maxkb | Maxkb | < 2.8.0 |
Related Weaknesses (CWE)
References
- https://github.com/1Panel-dev/MaxKB/commit/4d06362750b15390437f1d2e4d14ec79baef8Patch
- https://github.com/1Panel-dev/MaxKB/releases/tag/v2.8.0Release Notes
- https://github.com/1Panel-dev/MaxKB/security/advisories/GHSA-w9g4-q3gm-6q6wVendor Advisory
FAQ
What is CVE-2026-39418?
CVE-2026-39418 is a vulnerability with a CVSS score of 5.0 (MEDIUM). 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 authentica...
How severe is CVE-2026-39418?
CVE-2026-39418 has been rated MEDIUM with a CVSS base score of 5.0/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-39418?
Check the references section above for vendor advisories and patch information. Affected products include: Maxkb Maxkb.