# CVE-2026-86128: WatchGuard Fireware OS NULL pointer dereference in NetFlow IPv6 processing

Source: https://junglewise.ai/threats/cve-2026-86128-a-null-pointer-dereference-vulnerability-in-fireware-os-s-netflow  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-30. Updated: 2026-09-30  
License: CC BY 4.0 with a link back

CVE-2026-86128 · Severity: info · Published 2026-09-30

WatchGuard Fireware OS is network security firmware used in firewalls to protect corporate networks. A flaw in its NetFlow monitoring feature can be triggered by sending a specially crafted IPv6 packet from the network, causing the firewall to crash and stop protecting traffic, resulting in a denial of service.

Technologies: [Watchguard Fireware OS](https://junglewise.ai/threats/technologies/fireware-os). Vendors: [Watchguard](https://junglewise.ai/threats/vendors/watchguard).

## Quick answers

**Is CVE-2026-86128 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-86128 being exploited in the wild.

**How severe is CVE-2026-86128?** Informational severity, published 30 September 2026.

**Which products and versions are affected?** Watchguard Fireware OS 2026.3 before 2026.3.2, 2026.2 before 2026.2.3, 12.0 before 12.12.3; T15/T35 12.0 before 12.5.21.

**Is there a fix for CVE-2026-86128?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-86128 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-86128?** Check whether you run Watchguard Fireware OS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A NULL pointer dereference (CWE-476) in Fireware OS's NetFlow packet-processing engine can be triggered by a remote, unauthenticated attacker sending a malicious IPv6 packet. The vulnerability requires no authentication or user interaction and crashes the affected service, enabling denial of service via network-based attack. Patches are available in versions 2026.3.2, 2026.2.3, 12.12.3, and 12.5.21.

## Affected products

- WatchGuard Fireware OS 2026.3 before 2026.3.2, 2026.2 before 2026.2.3, 12.0 before 12.12.3; T15/T35 12.0 before 12.5.21

## Timeline

- 2026-09-29: disclosed

## References

- [https://psirt.watchguard.com/CVE-2026-86128](https://psirt.watchguard.com/CVE-2026-86128)

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