CVE-2021-23899Network attack vector

Arbitrary HTML/XML injection via unsafe delimiters

Published Jan 13, 2021 · Updated Aug 3, 2024

OWASP json-sanitizer before 1.2.2 allows remote attackers to inject arbitrary HTML or XML into embedding documents. Its sanitizer can emit closing SCRIPT tags and CDATA section delimiters from crafted input, breaking the surrounding document context. Exploitation requires control of data passed to the library and an embedding application that consumes the sanitizer output; impact can include script execution or markup injection in that document.

CVSS severity9.8
Critical
EPSS probability2.07%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OWASP json-sanitizer before 1.2.2 allows remote attackers to inject arbitrary HTML or XML into embedding documents. Its sanitizer can emit closing SCRIPT tags and CDATA section delimiters from crafted input, breaking the surrounding document context. Exploitation requires control of data passed to the library and an embedding application that consumes the sanitizer output; impact can include script execution or markup injection in that document.

The record

CVE
CVE-2021-23899
Published
Jan 13, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-611, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 13, 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

9.8NVDCVSS: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-611Improper Restriction of XML External Entity Reference
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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