CVE-2021-46143Network attack vector

Memory corruption via overflowing DTD group allocation

Published Jan 6, 2022 · Updated May 5, 2025

Integer overflow in Expat before 2.4.3 allows remote attackers to corrupt parser memory via a crafted XML document. In doProlog, doubling m_groupSize while growing the DTD group-connector buffer can wrap the allocation size and make realloc free the buffer. The gate is parsing a roughly 2 GiB XML document, after which the freed connector buffer exposes the process to a crash or memory corruption.

CVSS severity8.1
High
EPSS probability3.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in Expat before 2.4.3 allows remote attackers to corrupt parser memory via a crafted XML document. In doProlog, doubling m_groupSize while growing the DTD group-connector buffer can wrap the allocation size and make realloc free the buffer. The gate is parsing a roughly 2 GiB XML document, after which the freed connector buffer exposes the process to a crash or memory corruption.

The record

CVE
CVE-2021-46143
Published
Jan 6, 2022
Updated
May 5, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 6, 2022CVE publishedPublication date reported by the CVE source.
  2. May 5, 2025Record 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

8.1MITRECVSS:3.1/AC:H/AV:N/A:H/C:H/I:H/PR:N/S:U/UI:N
7.8NIST NVDCVSS:3.1/AV:L/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.

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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