# mcp-shell has a Secure Mode Allowlist Bypass via Git Shell Alias

Advisory record · `GHSA-74hp-mggr-hv58`

- **Identifiers:** `GHSA-74hp-mggr-hv58` · `CVE-2026-55582` · `GO-2026-6291`
- **State:** Confirmed
- **Severity:** CVSS 8.4 High
- **Critical:** No
- **Weakness (CWE):** [CWE-78](https://cwe.mitre.org/data/definitions/78.html)
- **Tags:** [Command injection](https://agentprime.io/advisories/tag/command-injection.md)
- **Published:** 25 Aug 2026
- **Updated:** 26 Aug 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 25 Aug 2026, 15:39 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/sonirico/mcp-shell` (Go): affected `<0.6.0`; fixed in `0.6.0`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> mcp-shell versions before 0.6.0 are vulnerable to a secure mode bypass. The allowlist validator does not block the "!" character, so an attacker who can call the shell_exec tool can pass a git command that defines a shell alias and runs arbitrary OS commands as the mcp-shell process user. Upgrade to version 0.6.0 or later.

Written 6 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 8.4 High, CVSS 3.1: `CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0027, the 19th percentile, on 12 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:48 UTC: First seen by agentprime
- 31 Oct 2026, 14:48 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-74hp-mggr-hv58)

## Sources

- [GitHub Advisory Database: GHSA-74hp-mggr-hv58](https://github.com/advisories/GHSA-74hp-mggr-hv58)
- [OSV: GHSA-74hp-mggr-hv58](https://osv.dev/vulnerability/GHSA-74hp-mggr-hv58)
- <https://github.com/sonirico/mcp-shell/security/advisories/GHSA-74hp-mggr-hv58>
- <https://github.com/sonirico/mcp-shell/pull/16>
- <https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f>
- <https://github.com/sonirico/mcp-shell>
- <https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-74hp-mggr-hv58>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-74hp-mggr-hv58/>. Everything for agents: <https://agentprime.io/llms.txt>.