CVE-2026-81433
Received Received - Intake

Stack-Based Buffer Overflow in WatchGuard Fireware OS

Publication date: 2026-09-30

Last updated on: 2026-09-30

Assigner: WatchGuard Technologies, Inc.

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.

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Meta Information

Published
2026-09-30
Last Modified
2026-09-30
Generated
2026-09-30
AI Q&A
2026-09-30
EPSS Evaluated
N/A
NVD
CVE-2026-81433
EUVD
EUVD-2026-89488

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
watchguard fireware_os From 2025.0 (inc) to 2026.2.3 (exc)
watchguard fireware_os From 2026.3 (inc) to 2026.3.2 (exc)
watchguard fireware_os From 12.0 (inc) to 12.12.3 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-121 A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
CWE-120 The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
CWE-787 The product writes data past the end, or before the beginning, of the intended buffer.

Attack-Flow Graph

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Executive Summary

This is a stack-based buffer overflow vulnerability in WatchGuard Fireware OS's DHCP fingerprinting daemon called fingerd. An unauthenticated attacker within adjacent network access can exploit it by sending a specially crafted DHCP packet to execute arbitrary code or crash the process.

Detection Guidance

Detecting this vulnerability requires monitoring for unusual DHCP traffic or crashes in the fingerd process. WatchGuard recommends checking Fireware OS versions against affected ranges (>=2026.3 but <2026.3.2, >=2025.0 but <2026.2.3, >=12.0 but <12.12.3). Inspect DHCP logs for malformed packets or process crashes.

Impact Analysis

An attacker could gain control of the affected system, execute malicious code, or cause denial-of-service conditions. This may lead to unauthorized access, data breaches, or disruption of network services if the device is compromised.

Compliance Impact

This vulnerability could lead to unauthorized access or data breaches, potentially violating GDPR's data protection requirements or HIPAA's security rules for protected health information. Compliance may be compromised if the vulnerability is exploited.

Mitigation Strategies

Immediately upgrade Fireware OS to versions 2026.3.2, 2026.2.3, or 12.12.3 or later. If upgrading is not possible, restrict adjacent network access to the DHCP fingerprinting daemon and monitor for suspicious activity.

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