# CVE-2026-97964: ppp_synctty: ensure a writeable skb header

> A missing writable header check in the Linux kernel PPP sync tty driver allows remote attackers to corrupt shared memory buffers via crafted PPPoE frames.

- **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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104238, BELL-CVE-2026-97964, DEBIAN-CVE-2026-97964, GHSA-59xx-49mr-rmvq, UBUNTU-CVE-2026-97964

## What is CVE-2026-97964?

CVE-2026-97964 is a memory corruption vulnerability in Linux, published on 25 Sep 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:

ppp_synctty: ensure a writeable skb header

ppp_sync_txmunge() checks headroom before prepending the address and
control bytes, but does not ensure that the skb header is writable.
A received skb can reach this function through PPP channel bridging
without passing through ppp_start_xmit(), which calls skb_cow_head().

For example, a PPPoE frame may share its buffer with a clone queued to
an AF_PACKET socket. If it is bridged to a synchronous tty channel, the
address/control bytes can overwrite data still visible to that socket.

Use skb_cow_head() to ensure both sufficient headroom and a writable
header.

## Which versions are affected by CVE-2026-97964?


## How do I fix CVE-2026-97964?

Apply the vendor's patch.

## Is CVE-2026-97964 being exploited?

There is no known exploitation of CVE-2026-97964 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97964 and fix it if it is affected.

What it is: CVE-2026-97964 is a memory corruption vulnerability in Linux, published on 25 Sep 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-2026-97964 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-2026-97964/ (Markdown: https://insights.sbomify.com/CVE-2026-97964/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97964
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97964
- OSV: https://osv.dev/vulnerability/CVE-2026-97964

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97964/
Summaries are generated and may contain mistakes; the official description above is the record.