CVE-2023-43634

/// Technical description

When sealing/unsealing the “vault” key, a list of PCRs is used, which defines which PCRs

are used.

In a previous project, CYMOTIVE found that the configuration is not protected by the secure

boot, and in response Zededa implemented measurements on the config partition that was

mapped to PCR 13.

In that process, PCR 13 was added to the list of PCRs that seal/unseal the key.

In commit “56e589749c6ff58ded862d39535d43253b249acf”, the config partition

measurement moved from PCR 13 to PCR 14, but PCR 14 was not added to the list of

PCRs that seal/unseal the key.

This change makes the measurement of PCR 14 effectively redundant as it would not affect

the sealing/unsealing of the key.

An attacker could modify the config partition without triggering the measured boot, this could

result in the attacker gaining full control over the device with full access to the contents of the

encrypted “vault”

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References