CVE-2022-48769 efi: runtime: avoid EFIv2 runtime services on Apple x86 machines
Linux kernel crashes on Apple x86 machines when calling EFI v2 runtime services, causing a denial of service.
- 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-2022-48769?
CVE-2022-48769 is a medium-severity denial of service vulnerability in Linux kernel, published on 20 Jun 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
efi: runtime: avoid EFIv2 runtime services on Apple x86 machines
Aditya reports [0] that his recent MacbookPro crashes in the firmware when using the variable services at runtime. The culprit appears to be a call to QueryVariableInfo(), which we did not use to call on Apple x86 machines in the past as they only upgraded from EFI v1.10 to EFI v2.40 firmware fairly recently, and QueryVariableInfo() (along with UpdateCapsule() et al) was added in EFI v2.00.
The only runtime service introduced in EFI v2.00 that we actually use in Linux is QueryVariableInfo(), as the capsule based ones are optional, generally not used at runtime (all the LVFS/fwupd firmware update infrastructure uses helper EFI programs that invoke capsule update at boot time, not runtime), and not implemented by Apple machines in the first place. QueryVariableInfo() is used to 'safely' set variables, i.e., only when there is enough space. This prevents machines with buggy firmwares from corrupting their NVRAMs when they run out of space.
Given that Apple machines have been using EFI v1.10 services only for the longest time (the EFI v2.0 spec was released in 2006, and Linux support for the newly introduced runtime services was added in 2011, but the MacbookPro12,1 released in 2015 still claims to be EFI v1.10 only), let's avoid the EFI v2.0 ones on all Apple x86 machines.
[0] https://lore.kernel.org/all/[email protected]/
Which versions are affected by CVE-2022-48769?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-48769?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2022-48769 being exploited?
There is no known exploitation of CVE-2022-48769 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-48769, GHSA-xprq-wxmv-vch9, UBUNTU-CVE-2022-48769.