CVE-2023-43635
HIGHVault Key Sealed With SHA1 PCRs The measured boot solution implemented in EVE OS leans on a PCR locking mechanism. Different parts of the system update different PCR values…
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Description
Vault Key Sealed With SHA1 PCRs
The measured boot solution implemented in EVE OS leans on a PCR locking mechanism.
Different parts of the system update different PCR values in the TPM, resulting in a unique value for each PCR entry.
These PCRs are then used in order to seal/unseal a key from the TPM which is used to encrypt/decrypt the “vault” directory.
This “vault” directory is the most sensitive point in the system and as such, its content should be protected.
This mechanism is noted in Zededa’s documentation as the “measured boot” mechanism, designed to protect said “vault”.
The code that’s responsible for generating and fetching the key from the TPM assumes that SHA256 PCRs are used in order to seal/unseal the key, and as such their presence is being checked.
The issue here is that the key is not sealed using SHA256 PCRs, but using SHA1 PCRs. This leads to several issues:
• Machines that have their SHA256 PCRs enabled but SHA1 PCRs disabled, as well as not sealing their keys at all, meaning the “vault” is not protected from an attacker.
• SHA1 is considered insecure and reduces the complexity level required to unseal the key in machines which have their SHA1 PCRs enabled.
An attacker can very easily retrieve the contents of the “vault”, which will effectively render the “measured boot” mechanism meaningless.
Affected Products
edge virtualization enginelinuxfoundationDetection & mitigation playbook
Vendor / applianceDetect
Inventory every linuxfoundation edge virtualization engine deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Fix
Apply the linuxfoundation edge virtualization engine security patch or hotfix for CVE-2023-43635 on the affected version, following the vendor advisory for your exact build.
Workarounds
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2023-43635 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2023-43635. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-43635 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2023-43635 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.