CVE-2021-23191Public exploit

Process crash via malformed embedded JPEG

Published Mar 2, 2022 · Updated Aug 3, 2024

NULL pointer dereference in HTMLDOC before 1.9.12 allows attackers to crash the process by supplying a crafted HTML document. The image_load_jpeg function installs a libjpeg error callback that returns instead of escaping error handling, so malformed embedded-JPEG decoding continues with invalid state and dereferences a null pointer. Processing attacker-supplied HTML containing the malformed image is required; the demonstrated consequence is termination of the HTMLDOC process.

CVSS severity7.8
High
EPSS probability1.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

NULL pointer dereference in HTMLDOC before 1.9.12 allows attackers to crash the process by supplying a crafted HTML document. The image_load_jpeg function installs a libjpeg error callback that returns instead of escaping error handling, so malformed embedded-JPEG decoding continues with invalid state and dereferences a null pointer. Processing attacker-supplied HTML containing the malformed image is required; the demonstrated consequence is termination of the HTMLDOC process.

The record

CVE
CVE-2021-23191
Published
Mar 2, 2022
Updated
Aug 3, 2024
Vendor
HTMLDOC Project
Product
HTMLDOC
Classifications
CWE-476
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=Fixed in htmldoc v1.9.12 and later.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

HTMLDOC Project · HTMLDOCversion=Fixed in htmldoc v1.9.12 and later.

Published CVSS scores

6.8NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8NVDCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo