CVE-2021-21899Public exploitNetwork attack vector

Code execution via unchecked DWG decompression copy

Published Nov 19, 2021 · Updated Aug 3, 2024

Heap buffer overflow in LibreCAD libdxfrw 2.2.0-rc2-19-ge02f3580 allows attackers to execute code via a crafted DWG file. The AC1021 header parser accepts a file-controlled decompressed length, and copyCompBytes21 writes that many bytes into a fixed 0x110-byte heap buffer without bounds checks. Exploitation requires a user or consuming application to open the malicious file and can run attacker-controlled code in that process.

CVSS severity8.8
High
EPSS probability2.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in LibreCAD libdxfrw 2.2.0-rc2-19-ge02f3580 allows attackers to execute code via a crafted DWG file. The AC1021 header parser accepts a file-controlled decompressed length, and copyCompBytes21 writes that many bytes into a fixed 0x110-byte heap buffer without bounds checks. Exploitation requires a user or consuming application to open the malicious file and can run attacker-controlled code in that process.

The record

CVE
CVE-2021-21899
Published
Nov 19, 2021
Updated
Aug 3, 2024
Vendor
LibreCAD
Product
libdxfrw
Classifications
CWE-119, CWE-787, T1204.002, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 19, 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?

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

  1. Affected versionversion=LibreCad libdxfrw 2.2.0-rc2-19-ge02f3580

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

LibreCAD · libdxfrwversion=LibreCad libdxfrw 2.2.0-rc2-19-ge02f3580

Published CVSS scores

8.8Cisco TalosCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:P/I:P/A:P
8.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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 exploitPublished

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-787Out-of-bounds Write
T1204.002User Execution Malicious File
T1203Exploitation for Client Execution

Public exploit references

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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