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CVE-2020-28279

flattenizer vulnerable to prototype pollution

9.8 CriticalFix available

Prototype pollution vulnerability in 'flattenizer' versions 0.0.5 through 1.0.5 allows an attacker to cause a denial of service and may lead to remote code execution.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

3.11%Up 1.4 points since Apr 14, 2021
90%50%10%1%

What each source reports

NVD Score used 9.8

Prototype pollution vulnerability in 'flattenizer' versions 0.0.5 through 1.0.5 allows an attacker to cause a denial of service and may lead to remote code execution.

Record
CVE-2020-28279
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0
7.5 HighAV:N/AC:L/Au:N/C:P/I:P/A:P
Updated
2026-11-02
CVE List No score

Prototype pollution vulnerability in 'flattenizer' versions 0.0.5 through 1.0.5 allows an attacker to cause a denial of service and may lead to remote code execution.

Record
CVE-2020-28279
Updated
2026-11-02
EUVDEUVD-2022-5400 No score

Prototype pollution vulnerability in 'flattenizer' versions 0.0.5 through 1.0.5 allows an attacker to cause a denial of service and may lead to remote code execution.

Record
EUVD-2022-5400
Updated
2026-11-03
GitHub AdvisoriesGHSA-vq33-26pr-r4h6 9.8

flattenizer vulnerable to prototype pollution

Overview

Prototype pollution vulnerability in ‘flattenizer’ versions 0.0.5 through 1.0.5 allows an attacker to cause a denial of service and may lead to remote code execution.

Details

The NPM module 'flattenizer' can be abused by Prototype Pollution vulnerability since the function 'unflatten()' did not check for the type of object before assigning value to the property. Due to this flaw an attacker could create a non-existent property or able to manipulate the property which leads to Denial of Service or potentially Remote code execution.

PoC Details

There is no validation before assigning the property to check whether the assigned argument is the Object's own property or not, the property polluted will be directly be assigned thereby polluting the Object prototype. Later in the code, if there is a check to validate polluted the valued would be substituted as "true" as it had been polluted.

var flattenizer = require("flattenizer")
flattenizer.unflatten({'__proto__.polluted': true});
console.log(polluted);
Record
GHSA-vq33-26pr-r4h6
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1321
Updated
2026-11-02
OSVGHSA-vq33-26pr-r4h6 9.8

flattenizer vulnerable to prototype pollution

Overview

Prototype pollution vulnerability in ‘flattenizer’ versions 0.0.5 through 1.0.5 allows an attacker to cause a denial of service and may lead to remote code execution.

Details

The NPM module 'flattenizer' can be abused by Prototype Pollution vulnerability since the function 'unflatten()' did not check for the type of object before assigning value to the property. Due to this flaw an attacker could create a non-existent property or able to manipulate the property which leads to Denial of Service or potentially Remote code execution.

PoC Details

There is no validation before assigning the property to check whether the assigned argument is the Object's own property or not, the property polluted will be directly be assigned thereby polluting the Object prototype. Later in the code, if there is a check to validate polluted the valued would be substituted as "true" as it had been polluted.

var flattenizer = require("flattenizer")
flattenizer.unflatten({'__proto__.polluted': true});
console.log(polluted);
Record
GHSA-vq33-26pr-r4h6
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1321
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
flattenizer
npm
0.0.5 to 1.0.5
1.1.1
flattenizer
npm
0.0.5 up to 1.1.1
1.1.1

History

History
RecordedChangedSources
facts
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-28279 is a critical vulnerability (CVSS 9.8) in Flattenizer Project Flattenizer, published December 29, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.11%, the 87th percentile. Fixed in flattenizer 1.1.1.

References

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