How severe is CVE-2026-86128?

CVE-2026-86128 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-86128 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-86128?

CVE-2026-86128 affects Watchguard Fireware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-86128?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-86128 published?

CVE-2026-86128 was published on 2026-09-30 and last updated on 2026-10-06.

CVE-2026-86128

CVE-2026-86128 is a high-severity vulnerability in Watchguard Fireware with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 8.2
EPSS exploit prediction: 0% (27th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-476
Affected product: Watchguard Fireware
Published: 2026-09-30
Last modified: 2026-10-06

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.

Frequently asked questions

What is CVE-2026-86128?: 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.
How severe is CVE-2026-86128?: CVE-2026-86128 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-86128 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-86128?: CVE-2026-86128 affects Watchguard Fireware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-86128?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-86128 published?: CVE-2026-86128 was published on 2026-09-30 and last updated on 2026-10-06.

References

https://psirt.watchguard.com/CVE-2026-86128

Affected products (1)

cpe:2.3:o:watchguard:fireware:*:*:*:*:*:*:*:*

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