CyberSecBulletin
CVE-2026-86128NVD status: Analyzed

Fireware OS: NULL Pointer Dereference

Published Updated By the CyberSecBulletin desk

CVE-2026-86128 is a high-severity NULL pointer dereference vulnerability in Fireware OS from WatchGuard, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 2026.3.2, 2026.2.3, 12.12.3 as the first without the flaw, so updating Fireware OS to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.36% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Fireware OS to 2026.3.2 or 2026.2.3 or 12.12.3 or 12.5.21, whichever matches your release line, or a later version.
  2. Update Fireware to 12.5.21 or 12.12.3 or 2026.2.3 or 2026.3.2, whichever matches your release line, or a later version.
  3. Read the advisory on psirt.watchguard.com for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
WatchGuardFireware OS2026.3 up to, but not including, 2026.3.2; 2025.0 up to, but not including, 2026.2.3; 12.0 up to, but not including, 12.12.3; 12.0 up to, but not including, 12.5.212026.3.2, 2026.2.3, 12.12.3, 12.5.21
WatchGuardFireware12.0 up to, but not including, 12.5.21; 12.12 up to, but not including, 12.12.3; 2025.0 up to, but not including, 2026.2.3; 2026.3 up to, but not including, 2026.3.212.5.21, 12.12.3, 2026.2.3, 2026.3.2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.08.2HighCNA
CVSS 3.17.5HighNVD

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: NULL Pointer Dereference

The product dereferences a pointer that it expects to be valid but is NULL.

How developers prevent this class of flaw

  • For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
  • Select a programming language that is not susceptible to these issues.
  • Check the results of all functions that return a value and verify that the value is non-null before acting upon it.

More NULL Pointer Dereference vulnerabilities (CWE-476)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Fireware OS

All Fireware OS vulnerabilities

Recent NULL Pointer Dereference vulnerabilities

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