CVE-2025-39681: Linux kernel · x86/cpu/hygon: Add missing resctrl_cpu_detect() in bsp_init helper
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in fb81222c1559f89bfe3aa1010f6d112531d55353 : update Linux kernel when convenient.
Data as of 5 Nov 2026, 21:48 UTC
Rated Medium by Threat Radar's AI analysis · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-05.
- Patch
- Available – fixed in fb81222c1559f89bfe3aa1010f6d112531d55353, d23264c257a70dbe021b43b3bc2ee16134cd2c69, d8df126349dad855cdfedd6bbf315bad2e901c2f +4
Exploitation evidence
Disclosed: evidence found.
CVE published 5 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 5 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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AI-suggested
A fix is available and has been applied in multiple Linux kernel commits identified by hashes fb81222c1559f89bfe3aa1010f6d112531d55353, d23264c257a70dbe021b43b3bc2ee16134cd2c69, d8df126349dad855cdfedd6bbf315bad2e901c2f, a9e5924daa954c9f585c1ca00358afe71d6781c4, 7207923d8453ebfb35667c1736169f2dd796772e, 873f32201df8876bdb2563e3187e79149427cab4, and 62f12cde10118253348a7540e85606869bd69432. Users should update affected Linux kernel versions to include these fixes. The affected version is Linux kernel 5.8. No additional mitigation is required beyond applying the official patch.
Description
A vulnerability in the Linux kernel's x86 CPU initialization for Hygon processors caused a division by zero fault during early boot. This occurred because the function resctrl_cpu_detect() was omitted from the Hygon BSP init helper, leading to uninitialized CPU cache scaling data when certain CPU features were present. The issue has been fixed by adding the missing function call in the affected code path.
References
- git.kernel.org/stable/c/62f12cde10118253348a7540e85606869bd69432 (opens in a new tab)
- git.kernel.org/stable/c/873f32201df8876bdb2563e3187e79149427cab4 (opens in a new tab)
- git.kernel.org/stable/c/fb81222c1559f89bfe3aa1010f6d112531d55353 (opens in a new tab)
- git.kernel.org/stable/c/7207923d8453ebfb35667c1736169f2dd796772e (opens in a new tab)
- git.kernel.org/stable/c/a9e5924daa954c9f585c1ca00358afe71d6781c4 (opens in a new tab)
- git.kernel.org/stable/c/d23264c257a70dbe021b43b3bc2ee16134cd2c69 (opens in a new tab)
- git.kernel.org/stable/c/d8df126349dad855cdfedd6bbf315bad2e901c2f (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/10/msg00008.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/10/msg00007.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-032379.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)