CVE-2025-39742: Linux kernel · RDMA: hfi1: fix possible divide-by-zero in find_hw_thread_mask()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · fixed in 5.15.0-1097.104~20.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1097.104~20.04.1, 5.15.0-1102.111~20.04.1, 5.15.0-1114.123~20.04.1 +59
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 11 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7909-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7933-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-7938-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8031-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
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.
References
- ubuntu.com/security/CVE-2025-39742 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-39742 (opens in a new tab)
- git.kernel.org/linus/59f7d2138591ef8f0e4e4ab5f1ab674e8181ad3a (opens in a new tab)
- git.kernel.org/stable/c/1a7cf828ed861de5be1aff99e10f114b363c19d3 (opens in a new tab)
- git.kernel.org/stable/c/31d0599a23efdbfe579bfbd1eb8f8c942f13744d (opens in a new tab)
- git.kernel.org/stable/c/4b4317b0d758ff92ba96f4e448a8992a6fe607bf (opens in a new tab)
- git.kernel.org/stable/c/59f7d2138591ef8f0e4e4ab5f1ab674e8181ad3a (opens in a new tab)
- git.kernel.org/stable/c/89fdac333a17ed990b41565630ef4791782e02f5 (opens in a new tab)
- git.kernel.org/stable/c/9b05e91afe948ed819bf87d7ba0fccf451ed79a6 (opens in a new tab)
- git.kernel.org/stable/c/9bba1a9994c523b44db64f63b564b4719ea2b7ef (opens in a new tab)
- git.kernel.org/stable/c/9d3211cb61a0773a2440d0a0698c1e6e7429f907 (opens in a new tab)
- git.kernel.org/stable/c/ac53f377393cc85156afdc90b636e84e544a6f96 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7933-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-5 (opens in a new tab)