CVE-2026-62312CWE-78

9Router: Authenticated RCE via Unvalidated MCP Plugin Arguments

High · published July 15, 2026

CVSS v3.1
8.8
EPSS
1%
Percentile
70.2
In the wild
Unconfirmed
What it is

9Router is an AI router & token saver. Prior to 0.5.2, 9Router allows a remote authenticated attacker to achieve arbitrary code execution on the host operating system by combining a Host header bypass of localhost-only routes with unvalidated MCP plugin args passed to child_process.spawn(), allowing malicious custom plugins to execute commands through /api/mcp//sse. This issue is fixed in version 0.5.2.

The record
Technical detail
CVSS v3.1
8.8 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.01297 · 70.2th percentile
Weakness
CWE-78 · Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Published
2026-07-15T20:53Z
EPSS history
Timeline
  • 15 JUL 20:53Z
    9Router: Authenticated RCE via Unvalidated MCP Plugin Arguments
    cvelistv5