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Vulnerability record · CVE-2026-55582 · published 25 August 2026

CVE-2026-55582: OS command injection vulnerability

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.

8.4 CVSS 3.1 High EPSS 0.27% · top 83.1% CWE-78 · OS command injection Deferred
8.4CVSS 3.1 base score
0.27%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
9 Sep 2026Last modified by NVD

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.

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

References

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

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Source: NIST National Vulnerability Database (record CVE-2026-55582), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.