CVE-2026-81097 json
rails-mcp-server 1.4.0 through 1.6.0 OS Command Execution via execute_ruby PTY Escape
published 2026-08-27 2 mo ago modified 2026-09-24 45 d ago also EUVD-2026-67025
- cvss
- 8.4
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 14%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- github.com/maquina-app/rails-mcp-server#59 pull request
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 2 mo ago
Exploit prediction
0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.6 | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N |
| CNA | 3.1 | 8.4 | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| CNA | 4.0 | 8.6 | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected products
- maquina-app rails-mcp-server
Classification
- Weakness
-
- CWE-78 Improper Neutralization of Special Elements used in an OS Command
- Technology feeds
References
-
github.com
/maquina-app/rails-mcp-server/pull/59
issue-tracking, patch
-
github.com
/maquina-app/rails-mcp-server
product
-
github.com
/maquina-app/rails-mcp-server/releases
release-notes
-
vulncheck.com
/advisories/rails-mcp-server-1.4.0-through-1.6.0-os-command-execution-via-execute-ruby-pty-escape
third-party-advisory
Sources
- CVE List CVE-2026-81097
- NVD CVE-2026-81097
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.