# CVE-2026-53003: pppoe: drop PFC frames

> An attacker can cause a denial of service by sending malformed PPPoE frames with compressed protocol fields, triggering unaligned access exceptions in the Linux kernel.

- **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:** 24 Jun 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-53003, DEBIAN-CVE-2026-53003, GHSA-7g5v-54rw-hq9g, ROOT-OS-DEBIAN-11-CVE-2026-53003, ROOT-OS-DEBIAN-12-CVE-2026-53003, ROOT-OS-UBUNTU-2204-CVE-2026-53003, ROOT-OS-UBUNTU-2404-CVE-2026-53003, UBUNTU-CVE-2026-53003

## What is CVE-2026-53003?

CVE-2026-53003 is a high-severity denial of service vulnerability in Linux kernel, published on 24 Jun 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:

pppoe: drop PFC frames

RFC 2516 Section 7 states that Protocol Field Compression (PFC) is NOT
RECOMMENDED for PPPoE. In practice, pppd does not support negotiating
PFC for PPPoE sessions, and the current PPPoE driver assumes an
uncompressed (2-byte) protocol field. However, the generic PPP layer
function ppp_input() is not aware of the negotiation result, and still
accepts PFC frames.

If a peer with a broken implementation or an attacker sends a frame with
a compressed (1-byte) protocol field, the subsequent PPP payload is
shifted by one byte. This causes the network header to be 4-byte
misaligned, which may trigger unaligned access exceptions on some
architectures.

To reduce the attack surface, drop PPPoE PFC frames. Introduce
ppp_skb_is_compressed_proto() helper function to be used in both
ppp_generic.c and pppoe.c to avoid open-coding.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-53003?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53003?

Apply the vendor's patch.

## Is CVE-2026-53003 being exploited?

There is no known exploitation of CVE-2026-53003 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53003 and fix it if it is affected.

What it is: CVE-2026-53003 is a high-severity denial of service vulnerability in Linux kernel, published on 24 Jun 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-2026-53003 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-53003/ (Markdown: https://insights.sbomify.com/CVE-2026-53003/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53003
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53003
- OSV: https://osv.dev/vulnerability/CVE-2026-53003

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53003/
Summaries are generated and may contain mistakes; the official description above is the record.