# CVE-2025-37992: net_sched: Flush gso_skb list too during ->change()

> A NULL pointer dereference in the Linux kernel network scheduler can cause a denial of service when reducing qdisc limits.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 May 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-37992, DEBIAN-CVE-2025-37992, GHSA-677f-c75x-79m2, ROOT-OS-DEBIAN-11-CVE-2025-37992, ROOT-OS-DEBIAN-12-CVE-2025-37992, ROOT-OS-UBUNTU-2204-CVE-2025-37992, ROOT-OS-UBUNTU-2404-CVE-2025-37992, UBUNTU-CVE-2025-37992

## What is CVE-2025-37992?

CVE-2025-37992 is a medium-severity vulnerability in Debian Debian Linux, published on 26 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

net_sched: Flush gso_skb list too during ->change()

Previously, when reducing a qdisc's limit via the ->change() operation, only
the main skb queue was trimmed, potentially leaving packets in the gso_skb
list. This could result in NULL pointer dereference when we only check
sch->limit against sch->q.qlen.

This patch introduces a new helper, qdisc_dequeue_internal(), which ensures
both the gso_skb list and the main queue are properly flushed when trimming
excess packets. All relevant qdiscs (codel, fq, fq_codel, fq_pie, hhf, pie)
are updated to use this helper in their ->change() routines.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2025-37992?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-37992?

Apply the vendor's patch.

## Is CVE-2025-37992 being exploited?

There is no known exploitation of CVE-2025-37992 in the wild and no public exploit code.

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## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-37992 and fix it if it is affected.

What it is: CVE-2025-37992 is a medium-severity vulnerability in Debian Debian Linux, published on 26 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-37992 in the wild and no public exploit code.

Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-37992/ (Markdown: https://insights.sbomify.com/CVE-2025-37992/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37992
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37992
- OSV: https://osv.dev/vulnerability/CVE-2025-37992

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37992/
Summaries are generated and may contain mistakes; the official description above is the record.