CVE-2025-39681 x86/cpu/hygon: Add missing resctrl_cpu_detect() in bsp_init helper
A missing initialization in the Hygon CPU driver causes a division by zero fault during boot, leading to a denial of service on affected Linux systems.
- 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-2025-39681?
CVE-2025-39681 is a medium-severity vulnerability in Debian Debian Linux, published on 5 Sep 2025. 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:
x86/cpu/hygon: Add missing resctrl_cpu_detect() in bsp_init helper
Since
923f3a2b48bd ("x86/resctrl: Query LLC monitoring properties once during boot")
resctrl_cpu_detect() has been moved from common CPU initialization code to the vendor-specific BSP init helper, while Hygon didn't put that call in their code.
This triggers a division by zero fault during early booting stage on our machines with X86_FEATURE_CQM* supported, where get_rdt_mon_resources() tries to calculate mon_l3_config with uninitialized boot_cpu_data.x86_cache_occ_scale.
Add the missing resctrl_cpu_detect() in the Hygon BSP init helper.
[ bp: Massage commit message. ]
Which versions are affected by CVE-2025-39681?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-39681?
Apply the vendor's patch.
Is CVE-2025-39681 being exploited?
There is no known exploitation of CVE-2025-39681 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-67043, AZL-73692, BELL-CVE-2025-39681, DEBIAN-CVE-2025-39681, GHSA-xfjg-jx94-93h4, ROOT-OS-DEBIAN-11-CVE-2025-39681 and 3 more.