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.

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Tue, 14 Apr 2026 01:15:00 +0000

Type Values Removed Values Added
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.
Title MaxKB: SSRF via sandbox network hook bypass
Weaknesses CWE-918
References
Metrics cvssV3_1

{'score': 5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-14T00:08:50.182Z

Reserved: 2026-04-07T00:23:30.595Z

Link: CVE-2026-39418

cve-icon Vulnrichment

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cve-icon NVD

Status : Received

Published: 2026-04-14T01:16:04.353

Modified: 2026-04-14T01:16:04.353

Link: CVE-2026-39418

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses