CVE-2025-39742 RDMA: hfi1: fix possible divide-by-zero in find_hw_thread_mask()
A divide-by-zero error in the Linux kernel's hfi1 RDMA driver can cause a system crash, requiring a kernel patch to prevent 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-2025-39742?
CVE-2025-39742 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 11 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:
RDMA: hfi1: fix possible divide-by-zero in find_hw_thread_mask()
The function divides number of online CPUs by num_core_siblings, and later checks the divider by zero. This implies a possibility to get and divide-by-zero runtime error. Fix it by moving the check prior to division. This also helps to save one indentation level.
Weakness: CWE-369
Which versions are affected by CVE-2025-39742?
It affects 2 products.
Linux distribution packages (2)
kernel-livepatch-SLE15-SP4_Update_45 SUSE:Linux Enterprise Live Patching 15 SP4 | All versions | 5-150400.2.1 |
kernel-livepatch-SLE15-SP5_Update_31 SUSE:Linux Enterprise Live Patching 15 SP5 | All versions | 4-150500.2.1 |
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-39742?
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-2025-39742 being exploited?
There is no known exploitation of CVE-2025-39742 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as BELL-CVE-2025-39742, DEBIAN-CVE-2025-39742, GHSA-3xq3-w9mf-92jr, ROOT-OS-DEBIAN-11-CVE-2025-39742, ROOT-OS-DEBIAN-12-CVE-2025-39742, ROOT-OS-UBUNTU-2204-CVE-2025-39742 and 4 more.