# CVE-2026-55580: mcp-shell — Security Disabled by Default in Bare-Binary Deploy Path + Shell Interpreter in Secure-Mode Allowlist

> An attacker can execute arbitrary OS commands via the shell_exec tool because security validation is disabled by default in the bare-binary deployment path.

- **Severity:** High 8.6 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** GHSA-f5pj-2738-996m, GO-2026-6292

## What is CVE-2026-55580?

CVE-2026-55580 is a high-severity command injection vulnerability in sonirico mcp-shell, published on 25 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-55580?

3 open source packages ship an affected version, including github.com/sonirico/mcp-shell.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/sonirico/mcp-shell` | Go | All versions | 0.6.0 |
| `github.com/sonirico/mcp-shell` | Go | All versions | 0.6.0 |
| `github.com/sonirico/mcp-shell` | Go | All versions | 0.6.0 |

## How do I fix CVE-2026-55580?

Upgrade github.com/sonirico/mcp-shell to 0.6.0 or later.

## Is CVE-2026-55580 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55580 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55580 and fix it if it is affected.

What it is: CVE-2026-55580 is a high-severity command injection vulnerability in sonirico mcp-shell, published on 25 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55580 exists.

Affected packages and fixed versions:
- github.com/sonirico/mcp-shell (Go): affected all versions; fixed in 0.6.0
- github.com/sonirico/mcp-shell (Go): affected all versions; fixed in 0.6.0
- github.com/sonirico/mcp-shell (Go): affected all versions; fixed in 0.6.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55580/ (Markdown: https://insights.sbomify.com/CVE-2026-55580/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55580
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55580
- OSV: https://osv.dev/vulnerability/CVE-2026-55580

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-55580/
Summaries are generated and may contain mistakes; the official description above is the record.