# CVE-2026-86128: Fireware OS NULL Pointer Dereference in NetFlow IPv6 Traffic Processing Allows Remote Denial of Service

> Remote attackers can cause denial of service on WatchGuard Fireware OS devices by sending crafted IPv6 packets to the NetFlow feature.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Sep 2026
- **Updated:** 30 Sep 2026
- **Also known as:** GHSA-pch3-5p8f-436q

## What is CVE-2026-86128?

CVE-2026-86128 is a high-severity vulnerability in Watchguard Fireware, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A NULL pointer dereference vulnerability in Fireware OS's NetFlow packet-processing feature allows a remote, unauthenticated attacker to cause a denial of service by sending a specially crafted IPv6 packet.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-86128?

It affects 1 product.


Products: Watchguard Fireware.

## How do I fix CVE-2026-86128?

No fix has been published for CVE-2026-86128 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-86128 being exploited?

There is no known exploitation of CVE-2026-86128 in the wild and no public exploit code.

## Other vulnerabilities in Watchguard Fireware

- [CVE-2022-26318](https://insights.sbomify.com/CVE-2022-26318/): WatchGuard Firebox and XTM Appliances Arbitrary Code Execution (critical 9.8, exploited in the wild)
- [CVE-2025-14733](https://insights.sbomify.com/CVE-2025-14733/): WatchGuard Firebox Out of Bounds Write (critical 9.3, exploited in the wild)
- [CVE-2025-9242](https://insights.sbomify.com/CVE-2025-9242/): WatchGuard Firebox Out-of-Bounds Write (critical 9.3, exploited in the wild)
- [CVE-2022-23176](https://insights.sbomify.com/CVE-2022-23176/): WatchGuard Firebox and XTM Privilege Escalation (high 8.8, exploited in the wild)
- [CVE-2022-31789](https://insights.sbomify.com/CVE-2022-31789/): Integer overflow in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-86128 and fix it if it is affected.

What it is: CVE-2026-86128 is a high-severity vulnerability in Watchguard Fireware, published on 29 Sep 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-2026-86128 in the wild and no public exploit code.

Affected product: Watchguard Fireware. 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-2026-86128/ (Markdown: https://insights.sbomify.com/CVE-2026-86128/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-86128
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-86128
- OSV: https://osv.dev/vulnerability/CVE-2026-86128

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-86128/
Summaries are generated and may contain mistakes; the official description above is the record.