CVE-2020-21818Public exploitNetwork attack vector

Memory corruption via htmlescape off-by-one writes

Published May 17, 2021 · Updated Jul 9, 2026

Heap buffer overflow in GNU LibreDWG 0.10.2641 allows context-dependent attackers to corrupt memory via a crafted DWG file. The dwg2SVG htmlescape routine in programs/escape.c performs off-by-one writes while escaping text from the input file, overrunning its heap allocation. A user or consuming application must process the crafted file; the published reproducer triggers the fault under AddressSanitizer, while code execution has not been demonstrated.

CVSS severity8.8
High
EPSS probability1.12%
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 context-dependent attackers to corrupt memory via a crafted DWG file. The dwg2SVG htmlescape routine in programs/escape.c performs off-by-one writes while escaping text from the input file, overrunning its heap allocation. A user or consuming application must process the crafted file; the published reproducer triggers the fault under AddressSanitizer, while code execution has not been demonstrated.

The record

CVE
CVE-2020-21818
Published
May 17, 2021
Updated
Jul 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

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 vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NVDAV: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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
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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