https://vulnerability.circl.lu Contains only the most 10 recent entries. http://www.rssboard.org/rss-specification python-feedgen en Thu, 01 Oct 2026 04:21:18 +0000 https://vulnerability.circl.lu/vuln/fkie_cve-2026-55581 <p>mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default Docker security.yaml includes /bin/bash in allowed_executables, while security.go validates only the first token and checkBlockedPatternsAndCommands does not reject the shell command-mode flag -c. A caller of the shell_exec MCP tool can provide the command argument `/bin/bash -c &lt;arbitrary-command&gt;`, which passes validation and reaches executor.go, where parseCommand and exec.CommandContext execute the arbitrary command as mcpuser outside the intended allowlist. This issue is fixed in version 0.6.0.</p> <p>mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default Docker security.yaml includes /bin/bash in allowed_executables, while security.go validates only the first token and checkBlockedPatternsAndCommands does not reject the shell command-mode flag -c. A caller of the shell_exec MCP tool can provide the command argument `/bin/bash -c &lt;arbitrary-command&gt;`, which passes validation and reaches executor.go, where parseCommand and exec.CommandContext execute the arbitrary command as mcpuser outside the intended allowlist. This issue is fixed in version 0.6.0.</p> https://vulnerability.circl.lu/vuln/fkie_cve-2026-55581 https://vulnerability.circl.lu/vuln/ghsa-3x77-wg38-92r3 <p><strong>Affected:</strong> Go: github.com/sonirico/mcp-shell</p> <p>### Summary</p> <p>`mcp-shell` ships a default Docker configuration (`security.yaml`) that includes `/bin/bash` in the `allowed_executables` allowlist. The command validator (`security.go`) only checks whether the first token of the supplied command matches an allowed executable; it does not inspect or reject shell command-mode flags such as `-c`. As a result, any MCP tool caller can send `command=/bin/bash -c &lt;arbitrary-command&gt;` to the `shell_exec` tool and execute commands that are not in the allowlist — including `id`, `env`, `curl`, `wget`, and any other binary present in the container. The bypass works with the default Docker image, requires no authentication, and requires no modifications to server configuration. Successful exploitation gives the attacker arbitrary OS command execution inside the container as `mcpuser`.</p> <p>### Details</p> <p>`mcp-shell` implements a *secure mode* in which command execution is restricted to an explicit allowlist of executables defined in `security.yaml`. The Docker image ships this file with the following entry:</p> <p>```yaml # security.yaml (line 29) allowed_executables: - &#34;ls&#34; - ... - &#34;/bin/bash&#34; # Only allow if you trust the arguments ```</p> <p>The comment itself acknowledges the risk, but the shipped default does not enforce any argument-level restriction. The validation logic in `security.go` is responsible for enforcing secure mode:</p> <p>```go // security.go:84-96 for _, allowed := range v.config.AllowedExecutables { if v.matchesExecutable(execut…</p> <p><strong>Affected:</strong> Go: github.com/sonirico/mcp-shell</p> <p>### Summary</p> <p>`mcp-shell` ships a default Docker configuration (`security.yaml`) that includes `/bin/bash` in the `allowed_executables` allowlist. The command validator (`security.go`) only checks whether the first token of the supplied command matches an allowed executable; it does not inspect or reject shell command-mode flags such as `-c`. As a result, any MCP tool caller can send `command=/bin/bash -c &lt;arbitrary-command&gt;` to the `shell_exec` tool and execute commands that are not in the allowlist — including `id`, `env`, `curl`, `wget`, and any other binary present in the container. The bypass works with the default Docker image, requires no authentication, and requires no modifications to server configuration. Successful exploitation gives the attacker arbitrary OS command execution inside the container as `mcpuser`.</p> <p>### Details</p> <p>`mcp-shell` implements a *secure mode* in which command execution is restricted to an explicit allowlist of executables defined in `security.yaml`. The Docker image ships this file with the following entry:</p> <p>```yaml # security.yaml (line 29) allowed_executables: - &#34;ls&#34; - ... - &#34;/bin/bash&#34; # Only allow if you trust the arguments ```</p> <p>The comment itself acknowledges the risk, but the shipped default does not enforce any argument-level restriction. The validation logic in `security.go` is responsible for enforcing secure mode:</p> <p>```go // security.go:84-96 for _, allowed := range v.config.AllowedExecutables { if v.matchesExecutable(execut…</p> https://vulnerability.circl.lu/vuln/ghsa-3x77-wg38-92r3