CVE-2022-42336 Security feature bypass in xen
Guests on AMD/Hygon hardware can bypass Spectre mitigations by underflowing the SSBD thread counter, disabling protections for other guests on the same core.
- 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-2022-42336?
CVE-2022-42336 is a low-severity vulnerability in Xen Xen, published on 17 May 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Mishandling of guest SSBD selection on AMD hardware The current logic to set SSBD on AMD Family 17h and Hygon Family 18h processors requires that the setting of SSBD is coordinated at a core level, as the setting is shared between threads. Logic was introduced to keep track of how many threads require SSBD active in order to coordinate it, such logic relies on using a per-core counter of threads that have SSBD active. When running on the mentioned hardware, it's possible for a guest to under or overflow the thread counter, because each write to VIRT_SPEC_CTRL.SSBD by the guest gets propagated to the helper that does the per-core active accounting. Underflowing the counter causes the value to get saturated, and thus attempts for guests running on the same core to set SSBD won't have effect because the hypervisor assumes it's already active.
Which versions are affected by CVE-2022-42336?
It affects 1 product.
Linux distribution packages (1)
xen openSUSE:Tumbleweed | All versions | 4.17.1_04-1.1 |
Products include Xen Xen.
How do I fix CVE-2022-42336?
Apply the vendor's patch.
Is CVE-2022-42336 being exploited?
There is no known exploitation of CVE-2022-42336 in the wild and no public exploit code.
Other vulnerabilities in Xen Xen
Sources
Also known as ALPINE-CVE-2022-42336, DEBIAN-CVE-2022-42336, GHSA-79pv-m8fc-mhfj, UBUNTU-CVE-2022-42336, openSUSE-SU-2024:12959-1.