CVE-2026-55582

HIGH 8.4

mcp-shell: Secure Mode Allowlist Bypass via Git Shell Alias

CVSS Score

8.4

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-78
Vendor	sonirico
Product	mcp-shell
Published	Aug 25, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Affected Versions

sonirico / mcp-shell

< 0.6.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/sonirico/mcp-shell/security/advisories/GHSA-74hp-mggr-hv58 github.com: https://github.com/sonirico/mcp-shell/pull/16 github.com: https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f github.com: https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0