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