deepmerge through 4.3.1 Prototype Poisoning via mergeObject (CVE-2026-93753) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-93753

deepmerge through 4.3.1 Prototype Poisoning via mergeObject

Answer in brief

CVE-2026-93753 records a Unknown severity vulnerability in deepmerge through 4.3.1 Prototype Poisoning via mergeObject. The current sources do not mark it as known exploited. The current feed maps TehShrike/deepmerge (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 18, 2026Updated Sep 18, 2026Source checked Sep 18, 2026First seen by HOL Sep 18, 2026Material review Sep 18, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps TehShrike/deepmerge (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
TehShrike/deepmergegeneric	0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for TehShrike/deepmerge.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Sep 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 18, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.