What is CVE-2021-24018?

CVE-2021-24018 is a medium-severity vulnerability in Fortinet Fortios, classified under Out-of-bounds Write. CVSS score: 4.3/10. Published 2021-08-04.

How severe is CVE-2021-24018?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Buffer overflow in Fortinet Fortios

CVE-2021-24018

A buffer underwrite vulnerability in the firmware verification routine of FortiOS before 7.0.1 may allow an attacker located in the adjacent network to potentially execute arbitrary code via a specifically crafted firmware image.

Vulnerability class: Buffer Overflow

Published 2021-08-04 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.010 (62.5th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 62nd percentile — 62.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000

Affected products

Fortinet Fortios — versions FortiOS before 7.0.1
Fortinet Fortios — versions 7.0.0

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

fortiguard.com/advisory/FG-IR-21-046 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-24018?: CVE-2021-24018 is a medium-severity vulnerability in Fortinet Fortios, classified under Out-of-bounds Write. CVSS score: 4.3/10. Published 2021-08-04.
How severe is CVE-2021-24018?: Medium severity. CVSS v3 base score is 4.3 out of 10.