CVE-2026-86104 Fireware OS Resource Exhaustion in Login Process Allows Denial of Service

What is CVE-2026-86104?

CVE-2026-86104 is a high-severity denial of service 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

An uncontrolled resource consumption vulnerability in the Fireware OS login process (wgagent) allows a remote, unauthenticated attacker to cause a denial of service by sending a specially crafted request.

Weakness: CWE-770, CWE-409, CWE-400

Which versions are affected by CVE-2026-86104?

It affects 1 product.

Products include Watchguard Fireware.

How do I fix CVE-2026-86104?

No fix has been published for CVE-2026-86104 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-86104 being exploited?

There is no known exploitation of CVE-2026-86104 in the wild and no public exploit code.

Other vulnerabilities in Watchguard Fireware

• CVE-2022-26318 WatchGuard Firebox and XTM Appliances Arbitrary Code Execution Exploited Critical 9.8
• CVE-2025-14733 WatchGuard Firebox Out of Bounds Write Exploited Critical 9.3
• CVE-2025-9242 WatchGuard Firebox Out-of-Bounds Write Exploited Critical 9.3
• CVE-2022-23176 WatchGuard Firebox and XTM Privilege Escalation Exploited High 8.8
• CVE-2022-31789 Integer overflow in n/a Critical 9.8

All Watchguard Fireware vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-44q2-m4gj-p5w4.