# CVE-2026-74668: packet: use consistent hard_header_len in TX_RING send path

> A race condition in the Linux kernel packet socket TX path can cause memory corruption or crashes due to inconsistent header length usage during concurrent reconfiguration.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 22 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-97371, BELL-CVE-2026-74668, DEBIAN-CVE-2026-74668, GHSA-j5cf-5xp4-r57f, UBUNTU-CVE-2026-74668

## What is CVE-2026-74668?

CVE-2026-74668 is a high-severity vulnerability in Linux, published on 22 Aug 2026. 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:

packet: use consistent hard_header_len in TX_RING send path

tpacket_snd() reads dev->hard_header_len independently for skb
allocation and header construction in tpacket_fill_skb(). Concurrent
netdevice reconfiguration can therefore make the reserved headroom
smaller than the amount later pushed, or make copylen - hard_header_len
negative.

Snapshot hard_header_len once before processing ring frames and use it
for the frame limit, headroom allocation, copy length, and skb
construction. Pass the snapshot to tpacket_fill_skb().

The separate SOCK_DGRAM consistency problem between hard_header_len and
header_ops->create is not addressed here.

## Which versions are affected by CVE-2026-74668?


## How do I fix CVE-2026-74668?

Apply the vendor's patch.

## Is CVE-2026-74668 being exploited?

There is no known exploitation of CVE-2026-74668 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74668 and fix it if it is affected.

What it is: CVE-2026-74668 is a high-severity vulnerability in Linux, published on 22 Aug 2026. 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-2026-74668 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-2026-74668/ (Markdown: https://insights.sbomify.com/CVE-2026-74668/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74668
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74668
- OSV: https://osv.dev/vulnerability/CVE-2026-74668

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74668/
Summaries are generated and may contain mistakes; the official description above is the record.