Updated advisory posts against rubysec/ruby-advisory-db@bf3d4cc

Author: jasnow

advisories/_posts/2026-08-27-CVE-2026-81097.md

@@ -0,0 +1,50 @@
+---
+layout: advisory
+title: 'CVE-2026-81097 (rails-mcp-server): The execute_ruby tool is documented as
+  a read-only Ruby sandbox'
+comments: false
+categories:
+- rails-mcp-server
+advisory:
+  gem: rails-mcp-server
+  cve: 2026-81097
+  ghsa: 247c-497m-jx82
+  url: https://nvd.nist.gov/vuln/detail/CVE-2026-81097
+  title: The execute_ruby tool is documented as a read-only Ruby sandbox
+  date: 2026-08-27
+  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.
+  cvss_v3: 8.4
+  cvss_v4: 8.6
+  unaffected_versions:
+  - "< 1.4.0"
+  patched_versions:
+  - ">= 1.6.1"
+  related:
+    url:
+    - https://nvd.nist.gov/vuln/detail/CVE-2026-81097
+    - https://rubygems.org/gems/rails-mcp-server/versions/2.0.0
+    - https://github.com/maquina-app/rails-mcp-server/releases/tag/v2.0.0
+    - https://rubygems.org/gems/rails-mcp-server/versions/1.6.1
+    - https://github.com/maquina-app/rails-mcp-server/releases/tag/v1.6.1
+    - https://github.com/maquina-app/rails-mcp-server/pull/59
+    - https://www.vulncheck.com/advisories/rails-mcp-server-1.4.0-through-1.6.0-os-command-execution-via-execute-ruby-pty-escape
+    - https://github.com/advisories/GHSA-247c-497m-jx82
+  notes: "- cvss_v3 and cvss_v4 from nvd.nist.gov URL.\n"
+---