bootc and ostree Unsigned Image Policy Bypass

Executive Summary

This vulnerability affects bootc and ostree systems. It allows unsigned OS content, staged under a permissive signature policy, to remain bootable even after the policy is hardened to reject unsigned images. When the system reboots or finalizes staged deployments, the unsigned content can be activated, leading to full host compromise.

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Detection Guidance

Check for staged deployments that may bypass signature policies by inspecting /etc/containers/policy.json and verifying if unsigned content was staged under a prior permissive policy. Use commands like ostree admin status or bootc status to review staged deployments. Ensure no unsigned deployments remain staged before policy hardening.

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Impact Analysis

An attacker could exploit this to execute unsigned, potentially malicious OS content as the host's root filesystem. This could lead to unauthorized access, data theft, or system takeover. Systems that never stage unsigned content or clear staged deployments after policy changes are not affected.

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Compliance Impact

This vulnerability could violate compliance requirements that mandate strict control over software integrity and security policies, such as GDPR's data protection principles or HIPAA's security rules. Unauthorized code execution risks data breaches and undermines secure configuration standards.

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Mitigation Strategies

Check for staged unsigned deployments and clear them before rebooting. Avoid staging unsigned content under permissive policies. No effective mitigation is currently available that meets Red Hat's criteria for ease of use or stability.

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