What is CVE-2021-26098?

CVE-2021-26098 is a medium-severity vulnerability in Fortinet Fortisandbox, classified under Use of Insufficiently Random Values. CVSS score: 5.3/10. Published 2021-08-04.

How severe is CVE-2021-26098?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Fortinet Fortisandbox

CVE-2021-26098

An instance of small space of random values in the RPC API of FortiSandbox before 4.0.0 may allow an attacker in possession of a few information pieces about the state of the device to possibly predict valid session IDs.

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

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.008 (55.3th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 55th percentile — 55.3% 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-330 — Use of Insufficiently Random Values

References

fortiguard.com/advisory/FG-IR-20-218 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-26098?: CVE-2021-26098 is a medium-severity vulnerability in Fortinet Fortisandbox, classified under Use of Insufficiently Random Values. CVSS score: 5.3/10. Published 2021-08-04.
How severe is CVE-2021-26098?: Medium severity. CVSS v3 base score is 5.3 out of 10.