CVE-2026-81433: Stack buffer overflow in WatchGuard Fireware OS DHCP fingerd · ZeroHour

CVE-2026-81433

large

Stack buffer overflow in WatchGuard Fireware OS DHCP fingerd

CVSS 4.0

8.7 high

EPSS

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Published

Sep 30, 2026 (9d ago)

Modified

Oct 1, 2026

AI analysis

CVE-2026-81433 is a stack-based buffer overflow (CWE-120, CWE-121, CWE-787) in the DHCP fingerprinting daemon fingerd on WatchGuard Fireware OS. An unauthenticated attacker on an adjacent network can trigger it by sending a specially crafted DHCP packet, with no user interaction required. Successful exploitation can run arbitrary code on the firewall or crash fingerd, with high impact to confidentiality, integrity, and availability of the device itself (CVSS 4.0 8.7). Affected Fireware OS version ranges are not stated in the provided data. It is not listed in CISA KEV, and no public proof-of-concept is known.

What to do: Apply WatchGuard's Fireware OS fix for CVE-2026-81433 as soon as the vendor publishes a patched build; the advisory data does not name a fixed version. Until then, keep untrusted hosts off segments where they can send DHCP to the firewall, and watch for fingerd crashes as a possible sign of exploit attempts.

Affected

WatchGuard Fireware OS (DHCP fingerprinting daemon fingerd)

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Estimated exposure

largeOn the order of 100,000 deployed Fireware appliances (estimate, not a census) — Order-of-magnitude estimate from WatchGuard's broad SMB and mid-market firewall deployment and typical public scan counts of internet-visible WatchGuard devices in the tens of thousands; total installed appliances are higher, and this flaw…

Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.

Description

A stack-based buffer overflow vulnerability in WatchGuard Fireware OS's DHCP fingerprinting daemon (fingerd) allows an unauthenticated attacker with adjacent network access to execute arbitrary code or crash the process by sending a specially crafted DHCP packet.

Weakness: CWE-120, CWE-121, CWE-787
Vector: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

NVD CVE.org GitHub PoCs EPSS (—)

CVE-2026-81433

In the news1 stories

WatchGuard fixes critical Fireware OS flaw allowing remote code execution