# CVE-2026-43329: netfilter: flowtable: strictly check for maximum number of actions

> A missing bounds check in Linux kernel netfilter flowtable allows attackers to trigger an integer overflow, potentially causing denial of service or code execution.

- **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:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43329, DEBIAN-CVE-2026-43329, GHSA-45q4-4828-537r, ROOT-OS-DEBIAN-11-CVE-2026-43329, ROOT-OS-UBUNTU-2204-CVE-2026-43329, ROOT-OS-UBUNTU-2404-CVE-2026-43329, UBUNTU-CVE-2026-43329

## What is CVE-2026-43329?

CVE-2026-43329 is a high-severity vulnerability in Linux kernel, published on 8 May 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:

netfilter: flowtable: strictly check for maximum number of actions

The maximum number of flowtable hardware offload actions in IPv6 is:

* ethernet mangling (4 payload actions, 2 for each ethernet address)
* SNAT (4 payload actions)
* DNAT (4 payload actions)
* Double VLAN (4 vlan actions, 2 for popping vlan, and 2 for pushing)
  for QinQ.
* Redirect (1 action)

Which makes 17, while the maximum is 16. But act_ct supports for tunnels
actions too. Note that payload action operates at 32-bit word level, so
mangling an IPv6 address takes 4 payload actions.

Update flow_action_entry_next() calls to check for the maximum number of
supported actions.

While at it, rise the maximum number of actions per flow from 16 to 24
so this works fine with IPv6 setups.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-43329?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43329?

Apply the vendor's patch.

## Is CVE-2026-43329 being exploited?

There is no known exploitation of CVE-2026-43329 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-2026-43329 and fix it if it is affected.

What it is: CVE-2026-43329 is a high-severity vulnerability in Linux kernel, published on 8 May 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-2026-43329 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-2026-43329/ (Markdown: https://insights.sbomify.com/CVE-2026-43329/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43329
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43329
- OSV: https://osv.dev/vulnerability/CVE-2026-43329

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43329/
Summaries are generated and may contain mistakes; the official description above is the record.