CVE-2021-1404Network attack vector

Scanner crash via PDF buffer over-read

Published Apr 8, 2021 · Updated Nov 8, 2024

Heap buffer over-read in the ClamAV PDF parser in versions 0.103.0 and 0.103.1 allows remote attackers to crash the scanner. The parser improperly tracks buffer sizes while processing a crafted PDF, causing a read beyond the allocated heap buffer. Any service that automatically submits attacker-controlled PDFs for scanning is exposed to an unauthenticated service interruption when its ClamAV scanning process crashes.

CVSS severity7.5
High
EPSS probability2.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer over-read in the ClamAV PDF parser in versions 0.103.0 and 0.103.1 allows remote attackers to crash the scanner. The parser improperly tracks buffer sizes while processing a crafted PDF, causing a read beyond the allocated heap buffer. Any service that automatically submits attacker-controlled PDFs for scanning is exposed to an unauthenticated service interruption when its ClamAV scanning process crashes.

The record

CVE
CVE-2021-1404
Published
Apr 8, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
ClamAV
Classifications
CWE-20, CWE-125, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.103.0
  2. Affected versionversion=0.103.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · ClamAVversion=0.103.0; version=0.103.1

Published CVSS scores

7.5Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-125Out-of-bounds Read
T1499.004Application or System Exploitation

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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