CVE-2026-55581
Raw vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-55581 is a high-severity OS Command Injection (CWE-78) vulnerability. Its CVSS base score is 8.4 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Command and Scripting Interpreter (T1059); ranked at the 27th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
This vulnerability is AI-related — categorised as AI Agent Protocols and Integrations; in the Protocol-Specific Risks risk domain.
The strongest mitigations our analysis identified map to CM-2 (Baseline Configuration) and CM-6 (Configuration Settings) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-65549
Vulnerability Data
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…
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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.
- CWE(s)
AI Security AnalysisAI
- AI Category
- AI Agent Protocols and Integrations
- Risk Domain
- Protocol-Specific Risks
- OWASP Top 10 for LLMs 2025
- None mapped
- Classification Reason
- Matched keywords: mcp, mcp, mcp
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 11 hardening rules · 6 OS baselines
V14.3.2V1.5.2V4.4.2V6.3.2
Mitigating Controls (NIST 800-53 r5) AI
Baseline configuration directly requires documenting and maintaining secure initial settings instead of insecure defaults.
Configuration settings mandate the most restrictive values be applied at initialization, eliminating reliance on insecure factory defaults.
Developer testing and evaluation can discover missing or incorrect command sanitization during development.
Input validation directly neutralizes or rejects special characters that would otherwise alter OS command structure.
Least privilege reduces the permissions available to any process that could be subverted by injected commands.
Least functionality restricts available OS commands and interpreters, limiting the blast radius of injection.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
PR.PS-06's SDLC practices directly require secure coding and input handling that blocks command-injection defects, yet the single broad outcome leaves many specific neutralization vectors and verification gaps unaddressed.
Pre-acquisition integrity checks can reject products known to ship with insecure defaults.
Hardened baselines and configuration management directly replace insecure defaults with secure settings.
Routine patching/maintenance can remediate known command-injection CVEs in dependencies (partial forward) but does nothing to stop developers from introducing improper neutralization in custom code (none reverse).
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Application security requirements can mandate strict, minimal allow-lists and input validation rules that prevent overly permissive lists.
Secure system architecture and engineering principles require explicit, least-privilege input validation designs that directly address permissive allow-lists.
Secure coding standards enforce rigorous input validation and reject unsafe values, mitigating permissive allow-list weaknesses.
Security testing and code review target insecure use of operating-system command interfaces, catching command-injection flaws introduced during development.
Requiring documented specification, testing, and acceptance of changes ensures that new or modified components are not initialized with insecure default settings that would otherwise be left in production.
Mandating secure baseline templates and immediate replacement of vendor defaults directly stops systems from being deployed with insecure factory settings that attackers can exploit.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248823 OL 8 must not have the telnet-server package installed. prevents CWE-1188
RHEL 7 (1 rule)
- V-204627 SNMP community strings on the Red Hat Enterprise Linux operating system must be changed from the default. prevents CWE-1188
Ubuntu 22.04 (1 rule)
- V-260529 Ubuntu 22.04 LTS must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements. prevents CWE-1188
Ubuntu 24.04 (1 rule)
- V-270708 Ubuntu 24.04 LTS must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements. prevents CWE-1188
Windows Server 2016 (1 rule)
- V-224972 Active Directory Group Policy objects must have proper access control permissions. prevents CWE-1188
Windows Server 2019 (1 rule)
- V-205741 Windows Server 2019 Active Directory Group Policy objects must have proper access control permissions. prevents CWE-1188