How severe is CVE-2021-3666?

CVE-2021-3666 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-3666 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3666?

CVE-2021-3666 affects Xml Body Parser Project Xml Body Parser. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3666?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-3666 published?

CVE-2021-3666 was published on 2021-09-13 and last updated on 2026-06-17.

CVE-2021-3666

CVE-2021-3666 is a critical-severity vulnerability in Xml Body Parser Project Xml Body Parser with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1321.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (67th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-1321
Affected product: Xml Body Parser Project Xml Body Parser
Published: 2021-09-13
Last modified: 2026-06-17

Description

body-parser-xml is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Frequently asked questions

What is CVE-2021-3666?: body-parser-xml is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
How severe is CVE-2021-3666?: CVE-2021-3666 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-3666 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3666?: CVE-2021-3666 affects Xml Body Parser Project Xml Body Parser. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3666?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-3666 published?: CVE-2021-3666 was published on 2021-09-13 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:xml_body_parser_project:xml_body_parser:*:*:*:*:*:node.js:*:*

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