# CVE-2026-72249: netfilter: flowtable: use dst in this direction when pushing IPIP header

> A Linux kernel netfilter flowtable bug causes incorrect headroom calculation when pushing IPIP headers, potentially leading to memory corruption or crashes.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-72249, GHSA-3xpj-q99r-5475, UBUNTU-CVE-2026-72249

## What is CVE-2026-72249?

CVE-2026-72249 is a critical memory corruption vulnerability in Linux, published on 15 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:

netfilter: flowtable: use dst in this direction when pushing IPIP header

When pushing the IPIP header, the route of the other direction is used
to calculate the headroom, use the route in this direction. Accessing
the other tuple to set the IP source and destination is fine because
this tuple does not provide such information to avoid storing redundant
information. However, this tuple already provides the dst for this
direction, this went unnoticed because this bug affects headroom and
iph->frag_off only at this stage.

## Which versions are affected by CVE-2026-72249?


## How do I fix CVE-2026-72249?

Apply the vendor's patch.

## Is CVE-2026-72249 being exploited?

There is no known exploitation of CVE-2026-72249 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72249 and fix it if it is affected.

What it is: CVE-2026-72249 is a critical memory corruption vulnerability in Linux, published on 15 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-2026-72249 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-2026-72249/ (Markdown: https://insights.sbomify.com/CVE-2026-72249/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72249
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72249
- OSV: https://osv.dev/vulnerability/CVE-2026-72249

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72249/
Summaries are generated and may contain mistakes; the official description above is the record.