How severe is CVE-2026-3987?

CVE-2026-3987 has a CVSS 4.0 base score of 8.6, rated high severity.

Is CVE-2026-3987 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-3987?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-3987 have an EU (EUVD) identifier?

Yes. CVE-2026-3987 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18090.

When was CVE-2026-3987 published?

CVE-2026-3987 was published on 2026-04-01 and last updated on 2026-06-17.

CVE-2026-3987

CVE-2026-3987 is a high-severity vulnerability with a CVSS 4.0 base score of 8.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: High (CVSS 4.0 base score 8.6)
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18090
Weakness: CWE-22
Published: 2026-04-01
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-3987?: 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.
How severe is CVE-2026-3987?: CVE-2026-3987 has a CVSS 4.0 base score of 8.6, rated high severity.
Is CVE-2026-3987 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-3987?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-3987 have an EU (EUVD) identifier?: Yes. CVE-2026-3987 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18090.
When was CVE-2026-3987 published?: CVE-2026-3987 was published on 2026-04-01 and last updated on 2026-06-17.

References

https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00009

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