# CVE-2025-68325: net/sched: sch_cake: Fix incorrect qlen reduction in cake_drop

> A logic error in the Linux kernel's CAKE qdisc can cause a NULL pointer dereference, leading to a system crash or denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Dec 2025
- **Updated:** 23 May 2026
- **Also known as:** BELL-CVE-2025-68325, DEBIAN-CVE-2025-68325, GHSA-vwv2-fc39-c5f6, ROOT-OS-DEBIAN-11-CVE-2025-68325, ROOT-OS-DEBIAN-12-CVE-2025-68325, ROOT-OS-DEBIAN-13-CVE-2025-68325, ROOT-OS-UBUNTU-2204-CVE-2025-68325, ROOT-OS-UBUNTU-2404-CVE-2025-68325, UBUNTU-CVE-2025-68325

## What is CVE-2025-68325?

CVE-2025-68325 is a vulnerability in Linux, published on 18 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

net/sched: sch_cake: Fix incorrect qlen reduction in cake_drop

In cake_drop(), qdisc_tree_reduce_backlog() is used to update the qlen
and backlog of the qdisc hierarchy. Its caller, cake_enqueue(), assumes
that the parent qdisc will enqueue the current packet. However, this
assumption breaks when cake_enqueue() returns NET_XMIT_CN: the parent
qdisc stops enqueuing current packet, leaving the tree qlen/backlog
accounting inconsistent. This mismatch can lead to a NULL dereference
(e.g., when the parent Qdisc is qfq_qdisc).

This patch computes the qlen/backlog delta in a more robust way by
observing the difference before and after the series of cake_drop()
calls, and then compensates the qdisc tree accounting if cake_enqueue()
returns NET_XMIT_CN.

To ensure correct compensation when ACK thinning is enabled, a new
variable is introduced to keep qlen unchanged.

## Which versions are affected by CVE-2025-68325?


## How do I fix CVE-2025-68325?

Apply the vendor's patch.

## Is CVE-2025-68325 being exploited?

There is no known exploitation of CVE-2025-68325 in the wild and no public exploit code.

Public exploit code:

- PoC CVE-2025-68325 (github_poc): https://github.com/n132/CVE-2025-68325

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68325 and fix it if it is affected.

What it is: CVE-2025-68325 is a vulnerability in Linux, published on 18 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-68325 in the wild and no public exploit code.

Affected product: 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-2025-68325/ (Markdown: https://insights.sbomify.com/CVE-2025-68325/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68325
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68325
- OSV: https://osv.dev/vulnerability/CVE-2025-68325

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68325/
Summaries are generated and may contain mistakes; the official description above is the record.