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CVE-2026-3987

WatchGuard Firebox Arbitrary File Write vis Path Traversal in Fireware Web UI

HIGH
7.2
CVSS Score
Published: April 1, 2026 at 09:32 PM UTC
Updated: October 26, 2026 at 09:10 PM UTC
1 product affected across 1 vendorFireware· also runs on 36 platforms

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Severity
HIGH7.2
Exploit prediction
EPSS 0.7%
SSVC
No known exploit

Description

A path traversal vulnerability in the Fireware OS Web UI on WatchGuard Firebox systems may allow a privileged authenticated remote attacker to execute arbitrary code in the context of an elevated system process.This issue affects Fireware OS 12.6.1 up to and including 12.11.8 and 2025.1 up to and including 2026.1.2.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Fireware· WatchGuard
95%
12.6.1 ≤ v < 12.122025.1 ≤ v < 2026.212.6.12025.1
Affected range stops below 12.12, so it looks safe — our inference, not a vendor statement
Affected range stops below 2026.2, so it looks safe — our inference, not a vendor statement
watchguard-firebox-cloud (environment) · watchguard-firebox-m270 (environment) · watchguard-firebox-m290 (environment) · watchguard-firebox-m295 (environment) · watchguard-firebox-m370 (environment) · watchguard-firebox-m390 (environment) · watchguard-firebox-m395 (environment) · watchguard-firebox-m440 (environment) · watchguard-firebox-m4600 (environment) · watchguard-firebox-m470 (environment) · watchguard-firebox-m4800 (environment) · watchguard-firebox-m495 (environment) · watchguard-firebox-m5600 (environment) · watchguard-firebox-m570 (environment) · watchguard-firebox-m5800 (environment) · watchguard-firebox-m590 (environment) · watchguard-firebox-m595 (environment) · watchguard-firebox-m670 (environment) · watchguard-firebox-m690 (environment) · watchguard-firebox-m695 (environment) · watchguard-firebox-nv5 (environment) · watchguard-firebox-t115-w (environment) · watchguard-firebox-t125 (environment) · watchguard-firebox-t125-w (environment) · watchguard-firebox-t145 (environment) · watchguard-firebox-t145-w (environment) · watchguard-firebox-t185 (environment) · watchguard-firebox-t20 (environment) · watchguard-firebox-t25 (environment) · watchguard-firebox-t40 (environment) · watchguard-firebox-t45 (environment) · watchguard-firebox-t55 (environment) · watchguard-firebox-t70 (environment) · watchguard-firebox-t80 (environment) · watchguard-firebox-t85 (environment) · watchguard-fireboxv (environment)

Runs on — not affected

The affected product only carries this flaw when running on these platforms. The platforms themselves are not vulnerable.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

Vendor Advisory
Source: cverecord
https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00009
Vendor AdvisoryBroken Link
Source: cverecord
https://psirt.watchguard.com/CVE-2026-3987

SSVC — Action Prioritization

SSVCNo known exploitNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.2HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-22

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