CVE-2026-3987
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA path traversal vulnerability in the Fireware OS Web UI on WatchGuard Firebox systems allows a privileged authenticated remote attacker to manipulate file paths and execute arbitrary code in the context of an elevated system process.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 2025.1, < 2026.2>= 12.6.1, < 12.12CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Identify the device modelCheck the physical device or access the management interface to confirm the system is a WatchGuard Firebox applianceAffected if The device is not a WatchGuard Firebox system - this CVE only affects Firebox appliances
-
Determine the Fireware OS versionAccess the Web UI or CLI and retrieve the firmware version (typically found in System > About or via CLI command 'fireware -v' or 'show version')Affected if The installed version is 12.11.8 or earlier, or 2026.1.2 or earlier, or any version prior to the patched releases
-
Verify Web UI is enabledCheck the Firebox management settings to confirm the Web UI (HTTP/HTTPS management interface) is turned onAffected if The Web UI is enabled and accessible - the vulnerability exists in the Web UI component
-
Check Web UI access controlsReview the management access settings to determine if the Web UI is exposed to untrusted networks or if non-administrator accounts have accessAffected if The Web UI is exposed to untrusted networks or accessible to accounts with fewer privileges than the ones needed for exploitation - the CVE requires a privileged authenticated attacker
-
Review administrator accountsAudit the list of accounts with administrative privileges on the FireboxAffected if There are privileged accounts whose credentials could be exploited - the CVE requires a privileged authenticated user
You are affected if you run a WatchGuard Firebox with Fireware OS version 12.11.8 or earlier (or 2026.1.2 or earlier) and have the Web UI enabled with privileged administrator accounts accessible to attackers.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data12.122026.2
Apply the vendor-supplied firmware update to a version beyond 12.11.8 or 2026.1.2 as appropriate, and restrict Web UI access to trusted privileged administrators only.
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-3987 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-3987 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data