CVE-2020-21816Public exploit

Crash via undersized HTML-escape buffer

Published May 17, 2021 · Updated Jul 9, 2026

Heap buffer overflow in GNU LibreDWG 0.10.2641 allows attackers to crash dwg2SVG by supplying a malformed DWG file. The htmlescape routine allocates only the input length plus ten bytes, then expands HTML metacharacters into longer entities without ensuring capacity. Processing the crafted file with dwg2SVG is required; the public proof of concept demonstrates a crash, while code execution is not established.

CVSS severity8.8
High
EPSS probability1.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in GNU LibreDWG 0.10.2641 allows attackers to crash dwg2SVG by supplying a malformed DWG file. The htmlescape routine allocates only the input length plus ten bytes, then expands HTML metacharacters into longer entities without ensuring capacity. Processing the crafted file with dwg2SVG is required; the public proof of concept demonstrates a crash, while code execution is not established.

The record

CVE
CVE-2020-21816
Published
May 17, 2021
Updated
Jul 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1204.002
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. May 17, 2021CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record 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 vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/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.

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No observations available

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

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1204.002User Execution: Malicious File

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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