CVE-2021-33603Network attack vector

Antivirus engine crash via fuzzed file scanning

Published Oct 8, 2021 · Updated Aug 3, 2024

Denial of service in F-Secure products using Atlant allows remote attackers to crash the antivirus engine via a fuzzed file. The AVPACK module crashes while scanning malformed file content instead of rejecting it safely. Delivery is remote, but published scoring indicates user interaction is required; the bounded consequence is interruption of antivirus scanning.

CVSS severity6.5
Medium
EPSS probability0.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in F-Secure products using Atlant allows remote attackers to crash the antivirus engine via a fuzzed file. The AVPACK module crashes while scanning malformed file content instead of rejecting it safely. Delivery is remote, but published scoring indicates user interaction is required; the bounded consequence is interruption of antivirus scanning.

The record

CVE
CVE-2021-33603
Published
Oct 8, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Oct 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
5.5F-SecureCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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