What is CVE-2026-8247?

CVE-2026-8247 is a high-severity vulnerability in Watchguard Firebox Cloud, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 8.8/10. Published 2026-07-03.

How severe is CVE-2026-8247?

High severity. CVSS v3 base score is 8.8 out of 10.

Buffer overflow in Watchguard Firebox Cloud

CVE-2026-8247

An Out-of-bounds Write vulnerability in WatchGuard Fireware OS may allow an unauthenticated attacker on the same local network segment to execute arbitrary code. This vulnerability affects Fireware OS 11.0 up to and including 11.12.4_Update1, 12.0 up to and including 12.12 and 2025.1 up to and including 2026.2.

Vulnerability class: Buffer Overflow

Published 2026-07-03 · last modified 2026-08-28.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.004 (30.0th percentile), scored 2026-10-05.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 30th percentile — 30.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001

Affected products

Weakness classification (CWE)

References

5d1c2695-1a31-4499-88ae-e847036fd7e3 (vendor-advisory, Vendor Advisory)
5d1c2695-1a31-4499-88ae-e847036fd7e3 (vendor-advisory, Broken Link)

Frequently asked questions

What is CVE-2026-8247?: CVE-2026-8247 is a high-severity vulnerability in Watchguard Firebox Cloud, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 8.8/10. Published 2026-07-03.
How severe is CVE-2026-8247?: High severity. CVSS v3 base score is 8.8 out of 10.