What is CVE-2021-33600?

CVE-2021-33600 is a medium-severity vulnerability in F-Secure Internet Gatekeeper, classified under Reachable Assertion. CVSS score: 5.4/10. Published 2021-09-28.

How severe is CVE-2021-33600?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Vulnerability in F-Secure Internet Gatekeeper

CVE-2021-33600

A denial-of-service (DoS) vulnerability was discovered in the web user interface of F-Secure Internet Gatekeeper. The vulnerability occurs because of an attacker can trigger assertion via malformed HTTP packet to web interface. An unauthenticated attacker could exploit this vulnerability by sending a large username parameter. A successful exploitation could lead to a denial-of-service of the product.

Published 2021-09-28 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.006 (49.0th percentile), scored 2026-10-31.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 49.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

F-Secure Internet Gatekeeper — versions 5 Series All Version
F-Secure Internet Gatekeeper

Weakness classification (CWE)

CWE-617 — Reachable Assertion

References

www.f-secure.com/en/business/programs/vulnerability-reward-program/hall-of-fame (Vendor Advisory)
www.f-secure.com/en/business/support-and-downloads/security-advisories/cve-2021… (Vendor Advisory)

Frequently asked questions

What is CVE-2021-33600?: CVE-2021-33600 is a medium-severity vulnerability in F-Secure Internet Gatekeeper, classified under Reachable Assertion. CVSS score: 5.4/10. Published 2021-09-28.
How severe is CVE-2021-33600?: Medium severity. CVSS v3 base score is 5.4 out of 10.