# CVE-2026-74696: tcp: fix TFO max_qlen accounting across reuseport migration

> A Linux kernel bug allows bypassing TCP Fast Open queue limits during listener migration, potentially causing resource exhaustion and denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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-97110, BELL-CVE-2026-74696, DEBIAN-CVE-2026-74696, GHSA-vp9r-6w4f-8wmq, UBUNTU-CVE-2026-74696

## What is CVE-2026-74696?

CVE-2026-74696 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:

tcp: fix TFO max_qlen accounting across reuseport migration

A listener's TCP_FASTOPEN max_qlen stops being accurate and lets through
far more pending Fast Open requests than it was configured for.

This only shows up with SO_REUSEPORT listener migration, where closing a
listener hands its still-pending TFO children over to a surviving one.

fastopenq.qlen is charged in tcp_fastopen_create_child() when the child
is created and uncharged in reqsk_fastopen_remove() when the handshake
completes.  The uncharge follows rsk_listener of the request the child
points at, and inet_reqsk_clone() has repointed the child at a new
request owned by the new listener, so the ++ and the -- land on two
different sockets.  The new listener's qlen drifts negative and its
limit no longer binds.

Charge the new listener during migration, like reqsk_queue_migrated()
already does for queue->young and queue->qlen.

## Which versions are affected by CVE-2026-74696?


## How do I fix CVE-2026-74696?

Apply the vendor's patch.

## Is CVE-2026-74696 being exploited?

There is no known exploitation of CVE-2026-74696 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74696 and fix it if it is affected.

What it is: CVE-2026-74696 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-2026-74696 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-2026-74696/ (Markdown: https://insights.sbomify.com/CVE-2026-74696/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74696
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74696
- OSV: https://osv.dev/vulnerability/CVE-2026-74696

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74696/
Summaries are generated and may contain mistakes; the official description above is the record.