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WatchGuard Fireware OS EUVDEUVD-2026-67336

| CVE-2026-78011 HIGH
Integer Underflow (CWE-191)
2026-08-27 WatchGuard GHSA-3fgq-vc6q-p4hg
Denial Of Service Integer Overflow Fireware Os Watchguard
8.7
CVSS 4.0 · Vendor: WatchGuard
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Severity by source

Vendor (WatchGuard) PRIMARY
8.7 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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
vuln.today AI
7.5 HIGH

Network-reachable IKE listener, no credentials required, no scope change; impact is solely availability crash of the VPN process.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (WatchGuard).

CVSS VectorVendor: WatchGuard

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
Patch available
Aug 28, 2026 - 04:16 EUVD
Analysis Generated
Aug 28, 2026 - 02:37 vuln.today
CVE Published
Aug 27, 2026 - 23:24 cve.org
HIGH 8.7

DescriptionCVE.org

An integer underflow vulnerability in the WatchGuard Fireware OS iked process allows a remote unauthenticated attacker to create a Denial of Service (DoS) condition in VPN processing by sending specially crafted network traffic.

AnalysisAI

Integer underflow in WatchGuard Fireware OS iked (IKE daemon) process enables remote unauthenticated attackers to crash VPN processing by sending specially crafted network traffic. The flaw (CWE-191) resides in the IKEv1/IKEv2 key exchange handler, meaning any internet-exposed WatchGuard appliance with VPN enabled is reachable from the network perimeter without credentials. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Vulnerability AssessmentAI

Exploitation Exploitation requires that the target WatchGuard Firebox appliance has VPN functionality enabled and that the iked process is reachable from the attacker's network position - typically UDP 500 and/or UDP 4500 exposed to the internet or an untrusted segment. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 score of 8.7 reflects AV:N/AC:L/AT:N/PR:N/UI:N with VA:H - a worst-case availability scenario requiring no special conditions or credentials. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Consult the WatchGuard PSIRT advisory at https://psirt.watchguard.com/CVE-2026-78011 for patched Fireware OS version details - no specific fix version is confirmed in available input data. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory all WatchGuard Fireware appliances running IKEv1/IKEv2 VPN, identify which are internet-facing, and document your remote access user population. …

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EUVD-2026-67336 vulnerability details – vuln.today
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