External risk intelligence

Sherlock GitHub Actions Command Injection Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-44590

This vulnerability exists within a GitHub Actions CI/CD workflow configuration used for development automation. It is a build-time or developer-centric process rather than a public-facing service, web application, or edge gateway. The risk is confined to the internal development pipeline and the automated testing environment.

OS Command Injection

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns a critical vulnerability in the Sherlock tool, which is used for identifying social media accounts. The flaw allows unauthorized command execution within the development environment, potentially enabling data exfiltration, without requiring any approvals or reviews. This impacts the integrity and security of the development pipeline.

Unauthorized commands can run on development systems.
It affects code development and testing integrity.
Confirm relevance and exposure for the development pipeline.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by submitting a pull request to a vulnerable project that uses GitHub Actions for continuous integration. The workflow, triggered by a pull request, would execute malicious commands on the CI runner. This could allow the attacker to access sensitive information, such as the GITHUB_TOKEN, which has broad permissions within the GitHub environment.

An attacker opens a pull request.
The pull request triggers a vulnerable workflow.
Arbitrary commands run on the CI runner.

Live Threat

Current exploitation, exposure, and threat context

When supported by the advisory, an attacker could execute arbitrary commands on the CI runner and exfiltrate the GITHUB_TOKEN by opening a pull request to the Sherlock project.

GitHub CI runner environment.
Pull request submission to the project.
Compromise of the CI runner and token.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Sherlock project's CI/CD pipeline is at risk, impacting those managing the development environment. The first step is to identify all instances of the affected GitHub Actions workflow, confirm its reachability within the CI/CD system, and then determine the owner responsible for the repository and its workflows to plan remediation.

Workflow owners should address the issue.
Verify CI/CD environment reachability.
Plan workflow remediation and testing.

Supplementary metadata

CVSS vector

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Frequently asked questions

What is Sherlock and how is it used?

Sherlock is an open-source tool designed to automate the process of finding social media accounts by username across numerous platforms. It is widely used by researchers and privacy advocates to aggregate public presence information. In this context, the tool includes GitHub Actions workflows to automate software testing and development tasks, which is where the security vulnerability resides.

What does CWE-78 mean for CVE-2026-44590?

CWE-78 is the classification for OS Command Injection. It means the software does not properly filter user-supplied input before passing it to a system shell. In this specific CVE, malicious commands hidden in a pull request are mistakenly interpreted as valid instructions by the automated build system, allowing unauthorized actions to occur on the runner.

How is this command injection triggered?

The flaw is triggered when an attacker submits a pull request to a repository using the affected workflow. The automation automatically executes the contained commands on the CI runner without requiring any human review, approval, or code merging. Simply viewing the repository or browsing the code does not trigger this vulnerability.

Is my organization at risk from this CVE?

Halo Surface Signal indicates that the risk is primarily confined to your internal development pipeline rather than external-facing production services. If you utilize the Sherlock project's CI/CD workflows, your development environment and automated testing integrity are potentially at stake, as the runner environment holds tokens with elevated access.

What should I do to secure my environment?

Begin by updating the Sherlock software to version 0.16.1 or later, which contains the fix for the workflow vulnerability. You should also audit your development repositories to ensure this specific GitHub Actions workflow is identified and updated. Coordinate with your repository owners to confirm the patch is applied and the CI/CD pipeline is secured against unauthorized command execution.

References

github.com/sherlock-project/sherlock/security/advisories/GHSA-v6…

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.