8.6

CVE-2026-3987: WatchGuard Firebox Arbitrary File Write vis Path Traversal in Fireware Web UI

Analyzed
Published 01-04-2026Last modified 10-08-2026

Vulnerability summary

CVE-2026-3987 is a high (CVSS 8.6) Path Traversal vulnerability in watchguard fireware. EPSS estimates a 1.06% chance of exploitation in the next 30 days, higher than 64.1% of scored vulnerabilities.

Overall risk
35/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.6/10
010
High · v4.0 (CVE.org)
EPSS score
1.06%
0%100%
Low · +0.38 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 01-04-2026
    PublishedVulnerability first disclosed.
  2. 10-08-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

1.06%

Chance of exploitation in the next 30 days

Percentile

64%

Versus all other CVEs

30-day change

Increase +0.38 pp

From 0.68% on 22-09-2026

22-09-202622-10-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Watchguard2 products
  • fireware≥ 2025.1, < 2026.2 | ≥ 12.6.1, < 12.12
  • fireware os≥ 2025.1, < 2026.2 | ≥ 12.6.1, < 12.12

1 vendor · 2 products

References

2 links