CVE-2023-43633 Debug Functions Unlockable Without Triggering Measured Boot
Attackers can bypass measured boot to enable debug features like SSH and VNC, gaining full device control without detection.
- 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-2023-43633?
CVE-2023-43633 is a high-severity 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/GlobalConfig/global.json”.
If the file exists, it overrides the existing configuration on the device on boot.
This allows an attacker to change the system’s configuration, which also includes some debug functions.
This could be used to unlock the ssh with custom “authorized_keys” via the “debug.enable.ssh” key, similar to the “authorized_keys” finding that was noted before.
Other usages include unlocking the usb to enable the keyboard via the “debug.enable.usb” key, allowing VNC access via the “app.allow.vnc” key, and more.
An attacker could easily enable these debug functionalities 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, thereby 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-2023-43633?
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 Lfedge Eve.
How do I fix CVE-2023-43633?
Upgrade github.com/lf-edge/eve to 0.0.0-20220708121648-5fef4d92e758 or later.
Is CVE-2023-43633 being exploited?
There is no known exploitation of CVE-2023-43633 in the wild and no public exploit code.
Other vulnerabilities in EVE OS
Sources
Also known as GHSA-4c4v-42hc-72p6, GO-2026-4428.