CVE-2026-55581
HIGHDescription
mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default Docker security.yaml includes /bin/bash in allowed_executables, while security.go validates only the first token and checkBlockedPatternsAndCommands does not reject the shell command-mode flag -c. A caller of the shell_exec MCP tool can provide the command argument `/bin/bash -c <arbitrary-command>`, which passes validation and reaches executor.go, where parseCommand and exec.CommandContext execute the arbitrary command as mcpuser outside the intended allowlist. This issue is fixed in version 0.6.0.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 27% of all known CVEs.
References
Related Vulnerabilities
Other CWE-78 (OS Command Injection) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2021-1498 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2014-6271 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2019-16920 | Critical | 9.8 | 100% | KEV | - |
| CVE-2022-44877 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2020-8515 | Critical | 9.8 | 100% | KEV | - |
| CVE-2020-9054 | Critical | 9.8 | 100% | KEV | Fix |
Common questions
How do I fix CVE-2026-55581?
No published fix for CVE-2026-55581 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-55581 being actively exploited?
Not that we know of. CVE-2026-55581 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.34% is the estimated probability that it will be exploited in the next 30 days. That is higher than 27% of all scored CVEs.
How severe is CVE-2026-55581?
CVE-2026-55581 has a CVSS v3 base score of 8.4, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-25.