SSRF in 1panel-Dev Maxkb
CVE-2026-39418
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.
Vulnerability class: SSRF (Server-Side Request Forgery)
EPSS: 0.002 (9.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L.
Affected products
- 1panel-dev Maxkb — versions < 2.8.0
- Maxkb
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-39418?
- CVE-2026-39418 is a medium-severity vulnerability in 1panel-Dev Maxkb, classified under Server-Side Request Forgery (SSRF). CVSS score: 5.0/10. Published 2026-04-14.
- How severe is CVE-2026-39418?
- Medium severity. CVSS v3 base score is 5.0 out of 10.