CVE-2021-25953Public exploitNetwork attack vector

Denial of service via unsafe deep merge

Published Jul 14, 2021 · Updated Aug 3, 2024

Prototype pollution in Panates Ltd. putil-merge 1.0.0 through 3.6.6 allows attackers to corrupt shared object state via a crafted object. The merge() function recursively copies a JSON-parsed proto property during deep merging without rejecting the special key, writing attacker-controlled properties onto Object.prototype. The polluted state causes a process crash or enables code execution only when consuming code exposes the merge path and contains a matching gadget.

CVSS severity9.8
Critical
EPSS probability2.96%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in Panates Ltd. putil-merge 1.0.0 through 3.6.6 allows attackers to corrupt shared object state via a crafted object. The merge() function recursively copies a JSON-parsed proto property during deep merging without rejecting the special key, writing attacker-controlled properties onto Object.prototype. The polluted state causes a process crash or enables code execution only when consuming code exposes the merge path and contains a matching gadget.

The record

CVE
CVE-2021-25953
Published
Jul 14, 2021
Updated
Aug 3, 2024
Vendor
Panates Ltd.
Product
putil-merge
Classifications
CWE-1321
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=3.6.6, 3.6.5, 3.6.4, 3.6.3, 3.6.2, 3.6.1, 3.6.0, 3.5.2, 3.5.1, 3.5.0, 3.4.2, 3.4.1, 3.3.0, 3.2.0, 3.1.4, 3.1.3, 3.1.2, 3.1.1, 3.1.0, 3.0.0, 2.2.0, 2.1.0, 2.0.2, 2.0.1, 2.0.0, 1.2.0, 1.1.5, 1.1.4, 1.1.3, 1.1.2, 1.1.1, 1.1.0, 1.0.2, 1.0.1, 1.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Panates Ltd. · putil-mergeversion=3.6.6, 3.6.5, 3.6.4, 3.6.3, 3.6.2, 3.6.1, 3.6.0, 3.5.2, 3.5.1, 3.5.0, 3.4.2, 3.4.1, 3.3.0, 3.2.0, 3.1.4, 3.1.3, 3.1.2, 3.1.1, 3.1.0, 3.0.0, 2.2.0, 2.1.0, 2.0.2, 2.0.1, 2.0.0, 1.2.0, 1.1.5, 1.1.4, 1.1.3, 1.1.2, 1.1.1, 1.1.0, 1.0.2, 1.0.1, 1.0.0

Published CVSS scores

9.8GitLab Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.

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No observations available

Sep 11, 2026Sep 17, 2026
Latest reporting daySep 17, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

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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