# CVE-2026-55582: mcp-shell: Secure Mode Allowlist Bypass via Git Shell Alias

> Attackers can execute arbitrary OS commands via Git shell aliases in mcp-shell, bypassing secure mode allowlists in default deployments.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 28 Aug 2026
- **Also known as:** GHSA-74hp-mggr-hv58, GO-2026-6291

## What is CVE-2026-55582?

CVE-2026-55582 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, 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.

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

## Which versions are affected by CVE-2026-55582?

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-2026-55582?

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

## Is CVE-2026-55582 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55582 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55582 and fix it if it is affected.

What it is: CVE-2026-55582 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-2026-55582 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-2026-55582/ (Markdown: https://insights.sbomify.com/CVE-2026-55582/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55582
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55582
- OSV: https://osv.dev/vulnerability/CVE-2026-55582

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55582/
Summaries are generated and may contain mistakes; the official description above is the record.