CVE-2021-3666Public exploitNetwork attack vector

Object prototype modification via crafted XML keys

Published Sep 13, 2021 · Updated Aug 3, 2024

Prototype pollution in Fiznool body-parser-xml before 2.0.3 allows remote authenticated users to alter object prototypes via crafted XML. The XML middleware assigns parsed data to req.body without first removing top-level proto, constructor, and prototype keys. Low-privileged access to an XML-accepting route is required, and the resulting effect depends on downstream use of polluted properties.

CVSS severity7.6
High
EPSS probability1.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in Fiznool body-parser-xml before 2.0.3 allows remote authenticated users to alter object prototypes via crafted XML. The XML middleware assigns parsed data to req.body without first removing top-level proto, constructor, and prototype keys. Low-privileged access to an XML-accepting route is required, and the resulting effect depends on downstream use of polluted properties.

The record

CVE
CVE-2021-3666
Published
Sep 13, 2021
Updated
Aug 3, 2024
Vendor
Fiznool
Product
body-parser-xml
Classifications
CWE-1321, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 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?

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

  1. Affected versionversion=unspecified <2.0.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Fiznool · body-parser-xmlversion=unspecified <2.0.3

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.6huntr.devCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
T1190Exploit Public-Facing Application

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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