Bug 2538136 (CVE-2026-93753)

Summary: CVE-2026-93753 deepmerge: deepmerge: Prototype Poisoning via mergeObject function
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in deepmerge. This vulnerability, known as prototype poisoning, allows an attacker to inject malicious properties into an application's object prototype. This occurs in the `mergeObject()` function due to insufficient validation of keys during object merging. By supplying specially crafted input, an attacker can cause applications to inherit unintended values, which may lead to arbitrary code execution or other impacts.
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Description OSIDB Bzimport 2026-09-22 17:14:56 UTC 
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.