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Fireware OS CVE-2026-81851

| EUVDEUVD-2026-67305 MEDIUM
Heap-based Buffer Overflow (CWE-122)
2026-08-27 WatchGuard GHSA-vjp6-wxgv-jj73
Buffer Overflow Denial Of Service Heap Overflow Fireware Os Watchguard
6.9
CVSS 4.0 · Vendor: WatchGuard
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Severity by source

Vendor (WatchGuard) PRIMARY
6.9 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/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
4.9 MEDIUM

Admin saves config over network (AV:N/PR:H); crash confined to iked on the same system with no data exposure (S:U/C:N/I:N).

3.1 AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:H/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
High
User Interaction
None
Scope
X

Lifecycle Timeline

2
Patch available
Aug 28, 2026 - 02:01 EUVD
Analysis Generated
Aug 27, 2026 - 23:51 vuln.today

DescriptionCVE.org

A heap-based buffer overflow vulnerability in Fireware OS's iked process allows an authenticated administrator to crash the IKE daemon (iked), resulting in a denial of service, by saving a specially crafted configuration.

AnalysisAI

Heap-based buffer overflow in WatchGuard Fireware OS's iked process allows an authenticated administrator to crash the IKE daemon by saving a specially crafted configuration, resulting in denial of service and disruption of IPsec VPN services. The CVSS 4.0 score of 6.9 with PR:H reflects the high-privilege requirement, meaning exploitation is gated behind valid administrator credentials. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Recon
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Vulnerability AssessmentAI

Exploitation Exploitation requires an authenticated administrator account on the WatchGuard Fireware OS management interface with the ability to modify and save device configurations - specifically IKE/IPsec-related configuration objects processed by the iked daemon. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N, score 6.9) appropriately captures the real-world risk profile. … 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 Apply the vendor-supplied patch per the WatchGuard PSIRT advisory at https://psirt.watchguard.com/CVE-2026-81851 - no exact fixed version number is independently confirmed from available data, so organizations must reference the advisory directly to identify the target upgrade version. … Detailed patch versions, workarounds, and compensating controls in full report.
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CVE-2026-81851 vulnerability details – vuln.today
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