CVE-2021-3766Network attack vector

Prototype pollution via unsafe __proto__ assignment

Published Sep 6, 2021 · Updated Aug 3, 2024

Prototype pollution in Objection.js before 2.2.16 allows attackers to alter object prototypes through crafted path or key input. The objectUtils set and zipObject functions accept proto components and assign through them, enabling prototype pollution in applications that pass attacker-controlled data. Exploitation requires an application to route untrusted input into these helpers; resulting integrity, availability, or confidentiality effects depend on downstream code.

CVSS severity9.8
Critical
EPSS probability1.47%
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 Objection.js before 2.2.16 allows attackers to alter object prototypes through crafted path or key input. The objectUtils set and zipObject functions accept proto components and assign through them, enabling prototype pollution in applications that pass attacker-controlled data. Exploitation requires an application to route untrusted input into these helpers; resulting integrity, availability, or confidentiality effects depend on downstream code.

The record

CVE
CVE-2021-3766
Published
Sep 6, 2021
Updated
Aug 3, 2024
Vendor
Vincit
Product
Objection.js
Classifications
CWE-1321, CWE-1321
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 6, 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 <2.2.16

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vincit · Objection.jsversion=unspecified <2.2.16

Published CVSS scores

9.8[email protected]CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5[email protected]AV:N/AC:L/Au:N/C:P/I:P/A:P
7.5[email protected]CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes
CWE-1321Improperly Controlled Modification of Object Prototype Attributes

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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