What is CVE-2021-41027?

CVE-2021-41027 is a high-severity vulnerability in Fortinet Fortiweb, classified under Out-of-bounds Write. CVSS score: 7.3/10. Published 2021-12-08.

How severe is CVE-2021-41027?

High severity. CVSS v3 base score is 7.3 out of 10.

Buffer overflow in Fortinet Fortiweb

CVE-2021-41027

A stack-based buffer overflow in Fortinet FortiWeb version 6.4.1 and 6.4.0, allows an authenticated attacker to execute unauthorized code or commands via crafted certificates loaded into the device.

Vulnerability class: Buffer Overflow

Published 2021-12-08 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.002 (4.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 4th percentile — 4.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Fortinet Fortiweb — versions FortiWeb 6.4.1, 6.4.0
Fortinet Fortiweb — versions 6.4.0, 6.4.1

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

fortiguard.com/advisory/FG-IR-21-134 (Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-41027?: CVE-2021-41027 is a high-severity vulnerability in Fortinet Fortiweb, classified under Out-of-bounds Write. CVSS score: 7.3/10. Published 2021-12-08.
How severe is CVE-2021-41027?: High severity. CVSS v3 base score is 7.3 out of 10.