# CVE-2026-98441: net/sched: act_ct: avoid modifying shared unconfirmed ct entry

> A use-after-free vulnerability in the Linux kernel's conntrack action allows attackers to potentially execute code or cause a denial of service via crafted network packets.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/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:** 18 Oct 2026
- **Updated:** 24 Oct 2026
- **Also known as:** AZL-109113, BELL-CVE-2026-98441, DEBIAN-CVE-2026-98441, GHSA-vvgr-4jx9-2c4x, UBUNTU-CVE-2026-98441

## What is CVE-2026-98441?

CVE-2026-98441 is a high-severity use after free vulnerability in Linux, published on 18 Oct 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:

net/sched: act_ct: avoid modifying shared unconfirmed ct entry

In a case where skb with an unconfirmed ct entry gets cloned, we may
end up processing both again but with different sets of extensions.

The series of events:

 1. The first clone wants to commit and runs the helpers wiring up
    the extension pointer into the expectation list.
 2. Then it looses the confirmation keeping the entry unconfirmed.
 3. Second clone now wants to commit labels or run NAT and adds the
    new extension for that breaking the pointer in the expectation
    list causing UAF on the destruction path later.

While this is possible to trigger, there should be no practical
network pipeline where we need to process both clones without
modifications in the same zone.  So, let's just reset the entry in
case for some reason we got an skb with a shared one.  This doesn't
affect any known use cases, but avoids any potential problems with
sharing and modification of the unconfirmed ct entry.

Unlike openvswitch module, act_ct allows for NAT without commit.
Changing that would be a uAPI break.  So, act_ct needs to reset on NAT
regardless of the commit flag to avoid reallocation of the extension
space.  This, however, doesn't really change the picture for sensible
networking cases as there should be no need to run the same packet
twice (before and after the clone) through conntrack without packet
header or zone changes and without commit.

The fixes tag points to the introduction of helpers, since that's the
main UAF trigger for the sharing.

## Which versions are affected by CVE-2026-98441?


## How do I fix CVE-2026-98441?

Apply the vendor's patch.

## Is CVE-2026-98441 being exploited?

There is no known exploitation of CVE-2026-98441 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98441 and fix it if it is affected.

What it is: CVE-2026-98441 is a high-severity use after free vulnerability in Linux, published on 18 Oct 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-2026-98441 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-2026-98441/ (Markdown: https://insights.sbomify.com/CVE-2026-98441/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98441
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98441
- OSV: https://osv.dev/vulnerability/CVE-2026-98441

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98441/
Summaries are generated and may contain mistakes; the official description above is the record.