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Vulnerability record · CVE-2026-55580 · published 25 August 2026

CVE-2026-55580: OS command injection vulnerability

mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, config.go initializes Security.Enabled to false, and when MCP_SHELL_SEC_CONFIG_FILE is unset, main.go starts the documented bare-binary deployment without a security policy. SecurityValidator.validateCommand in security.go then short-circuits and allows every command supplied to the shell_exec MCP tool, so an LLM connected over stdio can execute unrestricted OS commands as the mcp-shell process user. The README from-source installation and MCP client configuration omit MCP_SHELL_SEC_CONFIG_FILE, making the insecure state the documented default. This issue is fixed in version 0.6.0.

8.6 CVSS 4.0 High EPSS 0.20% · top 91.6% CWE-78 · OS command injection Deferred
8.6CVSS 4.0 base score
0.20%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, config.go initializes Security.Enabled to false, and when MCP_SHELL_SEC_CONFIG_FILE is unset, main.go starts the documented bare-binary deployment without a security policy. SecurityValidator.validateCommand in security.go then short-circuits and allows every command supplied to the shell_exec MCP tool, so an LLM connected over stdio can execute unrestricted OS commands as the mcp-shell process user. The README from-source installation and MCP client configuration omit MCP_SHELL_SEC_CONFIG_FILE, making the insecure state the documented default. This issue is fixed in version 0.6.0.

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

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-f5pj-2738-996m
https://github.com/sonirico/mcp-shell/security/advisories/GHSA-f5pj-2738-996m

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Source: NIST National Vulnerability Database (record CVE-2026-55580), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.