# CVE-2025-37932: sch_htb: make htb_qlen_notify() idempotent

> A flaw in the Linux kernel's HTB scheduler could cause a warning or instability when handling queue length notifications, potentially leading to denial of service.

- **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:** 20 May 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-72826, BELL-CVE-2025-37932, DEBIAN-CVE-2025-37932, GHSA-h35m-jp6f-245x, ROOT-OS-DEBIAN-11-CVE-2025-37932, ROOT-OS-DEBIAN-12-CVE-2025-37932, ROOT-OS-UBUNTU-2204-CVE-2025-37932, UBUNTU-CVE-2025-37932

## What is CVE-2025-37932?

CVE-2025-37932 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 20 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:

sch_htb: make htb_qlen_notify() idempotent

htb_qlen_notify() always deactivates the HTB class and in fact could
trigger a warning if it is already deactivated. Therefore, it is not
idempotent and not friendly to its callers, like fq_codel_dequeue().

Let's make it idempotent to ease qdisc_tree_reduce_backlog() callers'
life.

## Which versions are affected by CVE-2025-37932?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-37932?

Apply the vendor's patch.

## Is CVE-2025-37932 being exploited?

There is no known exploitation of CVE-2025-37932 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-37932 and fix it if it is affected.

What it is: CVE-2025-37932 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 20 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-2025-37932 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-2025-37932/ (Markdown: https://insights.sbomify.com/CVE-2025-37932/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37932
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37932
- OSV: https://osv.dev/vulnerability/CVE-2025-37932

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37932/
Summaries are generated and may contain mistakes; the official description above is the record.