CVE-2021-34119Public exploit

Process crash via empty-text heap under-read

Published Jul 18, 2023 · Updated Oct 28, 2024

Heap-buffer under-read in HTMLDOC 1.9.12 allows context-dependent attackers to crash the process via a crafted HTML input file. The parse_paragraph function subtracts one from the length of an empty text node and reads one byte before its heap buffer. Exploitation requires HTMLDOC to process the crafted file; the public proof of concept demonstrates an AddressSanitizer abort, while code execution remains undemonstrated.

CVSS severity7.8
High
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-buffer under-read in HTMLDOC 1.9.12 allows context-dependent attackers to crash the process via a crafted HTML input file. The parse_paragraph function subtracts one from the length of an empty text node and reads one byte before its heap buffer. Exploitation requires HTMLDOC to process the crafted file; the public proof of concept demonstrates an AddressSanitizer abort, while code execution remains undemonstrated.

The record

CVE
CVE-2021-34119
Published
Jul 18, 2023
Updated
Oct 28, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 18, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

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)
Vectorlocal
Privilegesunauthenticated
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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