TehShrike deepmerge up to 4.3.1 mergeObject prototype pollution

Summaryinfo

A vulnerability classified as critical was found in TehShrike deepmerge up to 4.3.1. Affected by this issue is the function mergeObject. The manipulation results in prototype pollution. This vulnerability is cataloged as CVE-2026-93753. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as critical, was found in TehShrike deepmerge up to 4.3.1. Affected is the function mergeObject. The manipulation with an unknown input leads to a prototype pollution vulnerability. CWE is classifying the issue as CWE-1321. The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

deepmerge through 4.3.1 contains a prototype poisoning vulnerability in the mergeObject() function that fails to properly validate keys being written to target objects. Attackers can supply malicious source objects in merge operations to inject attacker-controlled properties into the returned object's prototype, causing applications to inherit unintended values when accessing properties without own-property checks.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-93753 since 09/18/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/18/2026). This vulnerability is assigned to T1059 by the MITRE ATT&CK project.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• TehShrike

Name

• deepmerge

Version

• 4.3.0
• 4.3.1

Website

• Product: https://github.com/TehShrike/deepmerge/

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