critical CVSS 10

CVE-2026-42298·Docker vulnerability

Postiz is an AI social media scheduling tool. Prior to commit da44801, a "Pwn Request" vulnerability in the Build and Publish PR Docker Image workflow (.github/workflows/pr-docker-build.yml) allows any unauthenticated user to execute arbitrary code during the Docker build process and exfiltrate a highly privileged GITHUB_TOKEN (write-all permissions). This can be achieved simply by opening a Pull Request from a fork with a maliciously modified Dockerfile.dev. This issue has been patched via commit da44801.

Severity: critical
Software: Docker
Fixed in: 2.21.7
Published: 2026-05-08

Affected versions

Until: 2.21.7

Fixed in: 2.21.7

How to fix this CVE

Update Docker to version 2.21.7 or later to patch a critical vulnerability in the GitHub Actions workflow that could allow unauthorized code execution during container builds. This fix restricts access to sensitive GITHUB_TOKEN credentials by implementing proper authentication checks in the CI/CD pipeline. Ensure all Docker installations are updated immediately, as this vulnerability affects the build process itself and not runtime containers.

sudo dnf update docker-ce

Defensia detects this vulnerability

How to check if you are affected

Run 'docker --version' and verify the version is 2.21.7 or later
Check GitHub Actions workflow files in your repositories: examine .github/workflows/pr-docker-build.yml for proper GITHUB_TOKEN scoping and build context restrictions
Review GitHub Actions audit logs for any unexpected pull requests from forks that triggered Docker build workflows in the past 90 days
Verify the GitHub Actions secrets have been rotated by checking 'Settings > Secrets and variables > Actions' and confirming GITHUB_TOKEN permissions are set to 'Read repository contents' or lower, not write-all

FAQ

What is CVE-2026-42298?

This is a critical vulnerability in Docker's GitHub Actions workflow that permits unauthenticated attackers to inject malicious code during container image builds by submitting a forked pull request with a modified Dockerfile, potentially exposing highly privileged GitHub tokens with write-all permissions.

Is CVE-2026-42298 being actively exploited?

No, this vulnerability is not currently listed on CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available, but the attack surface is broad and remediation should be prioritized.

What versions of Docker are affected by CVE-2026-42298?

All versions of Docker prior to 2.21.7 are affected. Version 2.21.7 and later contain the necessary security patches.

How do I check if my server is vulnerable to CVE-2026-42298?

Run 'docker --version' and compare the output against 2.21.7. If your version is lower, your installation is vulnerable. Additionally, audit your GitHub Actions workflows to confirm build contexts are properly restricted.

Does Defensia detect CVE-2026-42298?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Docker is installed on a monitored server, CVE-2026-42298 will appear in your dashboard with remediation steps.

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References

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