RCE in Maquina-App Rails-Mcp-Server
CVE-2026-81097
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.
Vulnerability class: Command Injection (OS Command Injection)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.4 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.002 (13.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 13th percentile — 13.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.001
Affected products
Weakness classification (CWE)
References
- github.com/maquina-app/rails-mcp-server (product)
- github.com/maquina-app/rails-mcp-server/pull/59 (issue-tracking, patch)
- github.com/maquina-app/rails-mcp-server/releases (release-notes)
- www.vulncheck.com/advisories/rails-mcp-server-1.4.0-through-1.6.0-os-command-ex… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-81097?
- CVE-2026-81097 is a high-severity vulnerability in Maquina-App Rails-Mcp-Server, classified under OS Command Injection. CVSS score: 8.4/10. Published 2026-08-27.
- How severe is CVE-2026-81097?
- High severity. CVSS v3 base score is 8.4 out of 10.