CVE-2021-33600: A denial-of-service (DoS) vulnerability was discovered in the web user interface of F-Secure Internet Gatekeep

Routine

MEDIUM 5.4UPGRADE

CVE-2021-33600 is a medium-severity flaw (CVSS 5.4) affecting internet gatekeeper. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-617
Published	2021-09-28
Last modified	2026-06-17

Publisher (CNA): F-Secure · Vendor: f-secure

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-09-28 10:15 UTCPublished CVE record published
2026-06-17 03:54 UTCUpdated Record last modified

f-secure internet gatekeeper UPGRADE

Affected: >= 5.10 and <= 5.50.47

Fixed in: newer than 5.50.47

Safe to downgrade to: a release before 5.10

1. Check installed version

apt-cache policy internet-gatekeeper || rpm -q internet-gatekeeper || internet-gatekeeper --version

2. UPGRADE to newer than 5.50.47 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade internet-gatekeeper

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade internet-gatekeeper

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.10 (Debian / Ubuntu)

apt-cache madison internet-gatekeeper sudo apt install internet-gatekeeper=<VERSION_BEFORE_5.10> sudo apt-mark hold internet-gatekeeper

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list internet-gatekeeper sudo dnf downgrade internet-gatekeeper-<VERSION_BEFORE_5.10> sudo dnf versionlock add internet-gatekeeper

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-33600?

internet gatekeeper: upgrade to newer than 5.50.47. Exact commands for each OS are on this page.

Is CVE-2021-33600 being exploited?

CVE-2021-33600 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-33600 affect?

CVE-2021-33600 affects internet gatekeeper. Severity is medium (CVSS 5.4). 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 unauthent

How urgent is CVE-2021-33600?

Priority 31/100. No elevated risk signals yet.

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References

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