MaxKB: SSRF via sandbox network hook bypass_CVE-2026-39418

5 / 10

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

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.

Basic Information

ID CVE-2026-39418

Source GitHub_M

Published Apr 14, 2026 at 00:08

Affected Product

Vendor 1Panel-dev

Product MaxKB

Version < 2.8.0

Affected Versions 1Panel-dev MaxKB < 2.8.0

CWE Classification

CWE-918

References

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    "published": "2026-04-14T00:08:50.182Z",
    "modified": "2026-04-14T00:08:50.182Z",
    "type": "cve",
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