# CVE-2026-98287: pppoatm: ensure a writable skb header and linear data

> A local attacker can trigger memory corruption in the Linux kernel PPPoATM driver via bridged packets, potentially leading to code execution or privilege escalation.

- **Severity:** Not scored
- **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:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106313, BELL-CVE-2026-98287, DEBIAN-CVE-2026-98287, GHSA-m2p4-c77r-p2c7, UBUNTU-CVE-2026-98287

## What is CVE-2026-98287?

CVE-2026-98287 is a memory corruption vulnerability in Linux, published on 6 Oct 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:

pppoatm: ensure a writable skb header and linear data

In pppoatm_send(), LLC encapsulation checks whether there is sufficient
headroom for the 4-byte LLC header, but does not ensure that the skb header
is writable.

Normal transmit packets passing through ppp_start_xmit() have their header
unshared via skb_cow_head(). However, packets can also reach pppoatm_send()
via PPP channel bridging (PPPIOCBRIDGECHAN) without going through
ppp_start_xmit().

Use skb_cow_head() to ensure both sufficient headroom and a writable
header before pushing the LLC header.

While at it:
- Call pskb_may_pull(skb, 1) before inspecting skb->data[0] to prevent
  out-of-bounds reads on zero-length or non-linear frames (e.g. from
  bridging).
- Defer SC_COMP_PROT protocol compression until after pppoatm_may_send()
  succeeds. This eliminates the temporary skb allocation on admission failure
  and completely removes the fragile "undo" heuristic at the nospace label,
  avoiding any risk of reading uninitialized headroom or performing an
  unbalanced skb_push().

## Which versions are affected by CVE-2026-98287?


## How do I fix CVE-2026-98287?

Apply the vendor's patch.

## Is CVE-2026-98287 being exploited?

There is no known exploitation of CVE-2026-98287 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98287 and fix it if it is affected.

What it is: CVE-2026-98287 is a memory corruption vulnerability in Linux, published on 6 Oct 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-2026-98287 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-2026-98287/ (Markdown: https://insights.sbomify.com/CVE-2026-98287/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98287
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98287
- OSV: https://osv.dev/vulnerability/CVE-2026-98287

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98287/
Summaries are generated and may contain mistakes; the official description above is the record.