CVE-2021-23639Network attack vector

Remote code execution via front-matter JavaScript

Published Dec 10, 2021 · Updated Sep 17, 2024

Remote Code Execution in md-to-pdf before 5.0.0 allows remote attackers to execute code via crafted Markdown front matter. The converter passes front matter to gray-matter with its JavaScript engine enabled, so ---js content is evaluated as code. Exploitation requires control of Markdown processed by the converter; execution inherits converter-process privileges and can affect confidentiality, integrity, and availability.

CVSS severity9.8
Critical
EPSS probability5.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote Code Execution in md-to-pdf before 5.0.0 allows remote attackers to execute code via crafted Markdown front matter. The converter passes front matter to gray-matter with its JavaScript engine enabled, so ---js content is evaluated as code. Exploitation requires control of Markdown processed by the converter; execution inherits converter-process privileges and can affect confidentiality, integrity, and availability.

The record

CVE
CVE-2021-23639
Published
Dec 10, 2021
Updated
Sep 17, 2024
Vendor
Simon Haenisch
Product
md-to-pdf
Classifications
CWE-78, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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=unspecified <5.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Simon Haenisch · md-to-pdfversion=unspecified <5.0.0

Published CVSS scores

9.8SnykCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NVDAV:N/AC:L/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.

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

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-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1059.007Command and Scripting Interpreter: JavaScript

Public exploit references

No public exploit references are available in this record.

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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