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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-55582?
3 open source packages ship an affected version, including github.com/sonirico/mcp-shell.
| Package | 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.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is CVE-2026-55582 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55582 exists.
Sources
Also known as GHSA-74hp-mggr-hv58, GO-2026-6291.