# CVE-2026-74704: net/sched: sch_cake: drop WARN_ON(1) for malformed packets in ACK filter

> A malformed packet can trigger a kernel warning that causes a system panic if panic_on_warn is enabled, leading to denial of service.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-97050, BELL-CVE-2026-74704, DEBIAN-CVE-2026-74704, GHSA-5x69-69gj-gg3f, UBUNTU-CVE-2026-74704

## What is CVE-2026-74704?

CVE-2026-74704 is a high-severity denial of service vulnerability in Linux, published on 22 Aug 2026. 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: drop WARN_ON(1) for malformed packets in ACK filter

The sch_cake ACK filter parses packets to find the TCP header and filter
duplicated ACKs if the flow is backlogged. The parsing code contains a
WARN_ON(1) which can be triggered by a malformed IP header in certain
cases. Depending on the system configuration, this leads either to
either spamming dmesg with warnings, or a panic if panic_on_warn is set.

The code already correctly skips the offending packet in the branch that
triggers the warning, so the WARN_ON itself doesn't really serve any
purpose. So just drop it altogether to avoid the inconvenient side
effects.

## Which versions are affected by CVE-2026-74704?


## How do I fix CVE-2026-74704?

Apply the vendor's patch.

## Is CVE-2026-74704 being exploited?

There is no known exploitation of CVE-2026-74704 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74704 and fix it if it is affected.

What it is: CVE-2026-74704 is a high-severity denial of service vulnerability in Linux, published on 22 Aug 2026. 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-2026-74704 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-2026-74704/ (Markdown: https://insights.sbomify.com/CVE-2026-74704/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74704
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74704
- OSV: https://osv.dev/vulnerability/CVE-2026-74704

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74704/
Summaries are generated and may contain mistakes; the official description above is the record.