What is CVE-2021-26096?

CVE-2021-26096 is a medium-severity vulnerability in Fortinet Fortisandbox, classified under Out-of-bounds Write. CVSS score: 6.4/10. Published 2021-08-04.

How severe is CVE-2021-26096?

Medium severity. CVSS v3 base score is 6.4 out of 10.

Buffer overflow in Fortinet Fortisandbox

CVE-2021-26096

Multiple instances of heap-based buffer overflow in the command shell of FortiSandbox before 4.0.0 may allow an authenticated attacker to manipulate memory and alter its content by means of specifically crafted command line arguments.

Vulnerability class: Buffer Overflow

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

CVSS v3 metric

CVSS v3 base score 6.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:L.

EPSS exploit prediction

EPSS: 0.008 (53.8th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 53.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Fortinet Fortisandbox — versions FortiSandbox before 4.0.0
Fortinet Fortisandbox

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

fortiguard.com/advisory/FG-IR-20-188 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-26096?: CVE-2021-26096 is a medium-severity vulnerability in Fortinet Fortisandbox, classified under Out-of-bounds Write. CVSS score: 6.4/10. Published 2021-08-04.
How severe is CVE-2021-26096?: Medium severity. CVSS v3 base score is 6.4 out of 10.