CVE-2023-43631 SSH as Root Unlockable Without Triggering Measured Boot
Attackers can gain root SSH access by modifying an unprotected config file, bypassing measured boot integrity checks on EVE OS devices.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-43631?
CVE-2023-43631 is a high-severity authentication bypass vulnerability in EVE OS, published on 21 Sep 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
On boot, the Pillar eve container checks for the existence and content of “/config/authorized_keys”.
If the file is present, and contains a supported public key, the container will go on to open port 22 and enable sshd with the given keys as the authorized keys for root login.
An attacker could easily add their own keys and gain full control over the system without triggering the “measured boot” mechanism implemented by EVE OS, and without marking the device as “UUD” (“Unknown Update Detected”).
This is because the “/config” partition is not protected by “measured boot”, it is mutable, and it is not encrypted in any way.
An attacker can gain full control over the device without changing the PCR values, thus not triggering the “measured boot” mechanism, and having full access to the vault.
Note:
This issue was partially fixed in these commits (after disclosure to Zededa), where the config partition measurement was added to PCR13:
• aa3501d6c57206ced222c33aea15a9169d629141
• 5fef4d92e75838cc78010edaed5247dfbdae1889.
This issue was made viable in version 9.0.0 when the calculation was moved to PCR14 but it was not included in the measured boot.
Which versions are affected by CVE-2023-43631?
3 open source packages ship an affected version, including github.com/lf-edge/eve. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/lf-edge/eve Go | All versions | 0.0.0-20220708121648-5fef4d92e758 |
github.com/lf-edge/eve Go | All versions | 0.0.0-20220708121648-5fef4d92e758 |
github.com/lf-edge/eve Go | All versions | 0.0.0-20220708121648-5fef4d92e758 |
Products include Linuxfoundation Edge Virtualization Engine.
How do I fix CVE-2023-43631?
Upgrade github.com/lf-edge/eve to 0.0.0-20220708121648-5fef4d92e758 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2023-43631 being exploited?
There is no known exploitation of CVE-2023-43631 in the wild and no public exploit code.
Other vulnerabilities in EVE OS
Sources
Also known as GHSA-3mq9-xhgq-r7gj, GO-2026-4418.