Vulnerability · Published Aug 25, 2026 · Assigned by GitHub_M
CVE-2026-55582mcp-shell: Secure Mode Allowlist Bypass via Git Shell Alias
High 8.4
In plain English
A high-severity OS command injection in mcp-shell from sonirico. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/sonirico/mcp-shell | 0.6.0 | GHSA-74hp-mggr-hv58 |
| Go | github.com/sonirico/mcp-shell | 0.6.0 | GO-2026-6291 |
Affected products (as reported)
Weakness: CWE-78 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://github.com/sonirico/mcp-shell/security/advisories/GHSA-74hp-mggr-hv58 x_refsource_CONFIRM
- https://github.com/sonirico/mcp-shell/pull/16 x_refsource_MISC
- https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f x_refsource_MISC
- https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0 x_refsource_MISC