CVE-2021-23206Public exploit

Code execution via unbounded table COLSPAN

Published Mar 2, 2022 · Updated Aug 3, 2024

Stack-based buffer overflow in HTMLDOC before 1.9.12 allows local users to execute code by inducing processing of crafted HTML. The parse_table() function converts a COLSPAN attribute without bounding it to the remaining columns, then indexes fixed-size column arrays with that value. A user or document-processing workflow must open or convert attacker-supplied HTML; a successful trigger can crash the process or run code with its privileges.

CVSS severity7.8
High
EPSS probability1.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in HTMLDOC before 1.9.12 allows local users to execute code by inducing processing of crafted HTML. The parse_table() function converts a COLSPAN attribute without bounding it to the remaining columns, then indexes fixed-size column arrays with that value. A user or document-processing workflow must open or convert attacker-supplied HTML; a successful trigger can crash the process or run code with its privileges.

The record

CVE
CVE-2021-23206
Published
Mar 2, 2022
Updated
Aug 3, 2024
Vendor
HTMLDOC Project
Product
HTMLDOC
Classifications
CWE-121, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 2, 2022CVE 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Affects v1.9.12 and prior, Fixed in v1.9.12+

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

HTMLDOC Project · HTMLDOCversion=Affects v1.9.12 and prior, Fixed in v1.9.12+

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
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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