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CVE-2026-31236 simonw CVE debrief

CVE-2026-31236 is a critical code injection vulnerability in the llm CLI tool, specifically affecting versions up to 0.27.1. The vulnerability is caused by the unsafe use of the exec() function when handling the --functions command-line argument, which allows users to provide custom Python function definitions. An attacker can exploit this by crafting a malicious llm command with arbitrary Python code in the --functions argument and using social engineering to trick a victim into running it. This leads to arbitrary code execution on the victim's system, potentially granting the attacker full control. The vulnerability has a CVSS score of 9.8 and is considered critical.

Vendor
simonw
Product
llm
CVSS
CRITICAL 9.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-12
Original CVE updated
2026-06-30
Advisory published
2026-05-12
Advisory updated
2026-06-30

Who should care

Security teams and administrators responsible for systems and applications that utilize the llm CLI tool should be aware of this vulnerability. This includes organizations that use the llm tool for development, testing, or production environments. Additionally, developers and users of the llm tool should take immediate action to mitigate the risk of exploitation.

Technical summary

The llm CLI tool is vulnerable to a critical code injection attack via its --functions command-line argument. The tool uses the exec() function to execute user-provided Python code without proper sanitization, sandboxing, or security restrictions. This allows an attacker to inject arbitrary Python code, potentially leading to full control of the victim's system. The vulnerability is exacerbated by the fact that the --functions argument is intended for providing custom Python function definitions, making it a straightforward attack vector. The CVSS vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Defensive priority

This vulnerability should be prioritized for immediate attention due to its critical severity and potential for exploitation. Security teams should work closely with developers and system administrators to ensure that the vulnerability is patched or mitigated as soon as possible.

Recommended defensive actions

  • Apply the patch or update the llm CLI tool to a version that addresses this vulnerability.
  • Implement additional security controls, such as input validation and sanitization, to prevent similar vulnerabilities in the future.
  • Conduct thorough inventory checks to identify systems and applications that use the llm CLI tool.
  • Develop and implement compensating controls, such as monitoring and exception tracking, to detect and respond to potential exploitation attempts.
  • Educate developers and users about the risks associated with this vulnerability and the importance of secure coding practices.

Evidence notes

The CVE record and NVD detail provide official information about the vulnerability. Additional sources, including GitHub and Red Hat security advisories, offer further context and mitigation guidance. However, due to the limited information available, defenders should exercise caution and consider potential unknown affected scope.

Official resources

This article is AI-assisted and based on the supplied source corpus.