mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default security.yaml allows /usr/bin/git, while security.go omits ! from containsShellMetacharacters and containsDangerousShellConstructs and applies no per-executable argument policy. A caller of the shell_exec MCP tool can provide the command argument /usr/bin/git -c alias.pwn=!<arbitrary-command>, causing Git to create a shell alias and execute arbitrary OS commands as the mcp-shell process user.
The default Docker image runs as mcpuser with Git installed and secure mode enabled, so the bypass is exploitable in the default deployment without additional authentication beyond MCP connectivity. This issue is fixed in version 0.6.0.
Attack Parameters
Attack Vector
Local
Requires local access
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products
sonirico:mcp-shell
References 4
https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552…
security-advisories@github.com
https://github.com/sonirico/mcp-shell/pull/16
security-advisories@github.com
https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0
security-advisories@github.com
https://github.com/sonirico/mcp-shell/security/advisories/GHSA-74hp-mggr-hv58
security-advisories@github.com