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Vulnerability · Published Aug 27, 2026 · Assigned by VulnCheck

CVE-2026-81097rails-mcp-server 1.4.0 through 1.6.0 OS Command Execution via execute_ruby PTY Escape

High 8.4

In plain English

A high-severity OS command injection in rails-mcp-server from maquina-app. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities).

Severity (CVSS 3.1)8.4High
Exploit odds (30 days)0.2%top 85.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

The execute_ruby tool is documented as a read-only Ruby sandbox and is enforced by a pattern denylist together with replacements for the process-spawning methods on Kernel. The pseudo-terminal library's spawn entry points are neither in the denylist nor replaced, so a normal tool call could reach them and start a shell, executing commands as the account running the server and outside the guarded methods. The denylist was introduced with the tool in 1.4.0 and never covered those entry points through 1.6.0. Version 1.6.1 restricts the requires the sandbox permits to a data-only list and blocks dynamic dispatch to execution entry points; 2.0.0 removes the tool.

Affected products (as reported)

VendorProductVersions
maquina-app rails-mcp-server 1.4.0 – through 1.6.0

Weakness: CWE-78 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References