CVE-2025-21800: Linux kernel · net/mlx5: HWS, fix definer's HWS_SET32 macro for negative offset
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High.
Data as of 29 Oct 2026, 23:41 UTC
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Feb 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 29 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinux-raspi-realtimepkg:deb/ubuntu/linux-raspi-realtime?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-allwinner-5.19pkg:deb/ubuntu/linux-allwinner-5.19?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-aws-5.19pkg:deb/ubuntu/linux-aws-5.19?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-aws-6.2pkg:deb/ubuntu/linux-aws-6.2?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-aws-6.5pkg:deb/ubuntu/linux-aws-6.5?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-azure-5.19pkg:deb/ubuntu/linux-azure-5.19?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix for this vulnerability is available as it has been resolved in the affected Linux kernel versions listed. Users should update to patched kernel versions to remediate the issue. Since this is not a cloud service, manual patching is required. No indication of no-action or automatic mitigation is provided, so applying the official kernel updates is recommended.
Description
CVE-2025-21800 is a high-severity vulnerability in the Linux kernel's net/mlx5 driver related to the HWS_SET32 macro. The issue arises when the macro is used with a negative bit offset, causing a shift-out-of-bounds error detected by UBSAN (Undefined Behavior Sanitizer). This flaw affects multiple specific versions of the Linux kernel, including various Ubuntu HWE edge releases. The vulnerability has a CVSS score of 7.8, indicating a significant impact on confidentiality, integrity, and availability.
References
- ubuntu.com/security/CVE-2025-21800 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-21800 (opens in a new tab)
- git.kernel.org/linus/be482f1d10da781db9445d2753c1e3f1fd82babf (opens in a new tab)
- git.kernel.org/stable/c/69c676c0ded472713e6d1b3a456b3c4f52f66f0e (opens in a new tab)
- git.kernel.org/stable/c/92cff996624c4757d5bbace3dfa3f1567ba94143 (opens in a new tab)
- git.kernel.org/stable/c/be482f1d10da781db9445d2753c1e3f1fd82babf (opens in a new tab)