# CVE-2026-72429: ipv6: ioam: fix type confusion of dst_entry

> A type confusion vulnerability in the Linux kernel IPv6 IOAM module allows invalid pointer access, potentially leading to code execution or denial of service.

- **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:** BELL-CVE-2026-72429, DEBIAN-CVE-2026-72429, GHSA-34fv-pgg7-6wvm, UBUNTU-CVE-2026-72429

## What is CVE-2026-72429?

CVE-2026-72429 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:

ipv6: ioam: fix type confusion of dst_entry

IOAM uses a dummy dst_entry(null_dst) to mark that the destination should
not be changed after the transformation. This dst is stored in the IOAM lwt
state and may be passed to dst_cache_set_ip6().

However, the IPv6 dst cache path eventually calls rt6_get_cookie(), which
treats the dst_entry as part of a struct rt6_info. Since the null_dst was
embedded directly as a struct dst_entry in struct ioam6_lwt, this resulted
in an invalid cast and rt6_get_cookie() reading fields from the wrong
object.

In practice, the wrong cookie is not used while dst->obsolete is zero, but
rt6_get_cookie() may also access per-cpu value when rt->sernum is
zero. In this case, rt->sernum aliases ioam6_lwt::cache::reset_ts, which
can become zero, making this a potential invalid pointer access.

Fix this by embedding a full struct rt6_info for the dummy IPv6 route and
passing its dst member to the dst APIs.

## Which versions are affected by CVE-2026-72429?


## How do I fix CVE-2026-72429?

Apply the vendor's patch.

## Is CVE-2026-72429 being exploited?

There is no known exploitation of CVE-2026-72429 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72429 and fix it if it is affected.

What it is: CVE-2026-72429 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-2026-72429 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-2026-72429/ (Markdown: https://insights.sbomify.com/CVE-2026-72429/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72429
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72429
- OSV: https://osv.dev/vulnerability/CVE-2026-72429

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72429/
Summaries are generated and may contain mistakes; the official description above is the record.