CVE-2021-31347Public exploitNetwork attack vector

Crash via malformed DOCTYPE parsing

Published Apr 16, 2021 · Updated Aug 3, 2024

Out-of-bounds write in ezXML 0.8.6 allows remote attackers to crash applications via crafted XML files when parsed. The ezxml_parse_str() DOCTYPE loop advances past the mmap-created input region when strcspn() finds no closing delimiter, then writes a NUL byte through the invalid pointer. Exploitation requires an application to parse attacker-supplied XML, and the documented consequence is process crash or service interruption.

CVSS severity6.5
Medium
EPSS probability1.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in ezXML 0.8.6 allows remote attackers to crash applications via crafted XML files when parsed. The ezxml_parse_str() DOCTYPE loop advances past the mmap-created input region when strcspn() finds no closing delimiter, then writes a NUL byte through the invalid pointer. Exploitation requires an application to parse attacker-supplied XML, and the documented consequence is process crash or service interruption.

The record

CVE
CVE-2021-31347
Published
Apr 16, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-91, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 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?

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

6.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NVDAV:N/AC:M/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.

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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-91XML Injection
T1499Endpoint Denial of Service

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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