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Response snapshot Oct 27, 2026, 23:56 UTC

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VulnerabilityCVE-2026-93753

deepmerge mergeObject() allows prototype poisoning of returned objects

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.

At a glance

Exploited
Not known
Severity
2.7 Low (CVSS 4.0)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Consult the exact GitHub advisory for affected versions, mitigation, and patch availability.

Read GitHub-reviewed advisory GHSA-gcqx-w48m-w2h4 (opens a new tab)

What happened

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.

Affected package ranges reported by GitHub: deepmerge: >= 4.2.0, <= 4.3.1

Scores and how they were measured

CVSS base severity

2.7

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-gcqx-w48m-w2h4 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-gcqx-w48m-w2h4, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 27). deepmerge mergeObject() allows prototype poisoning of returned objects (CVE-2026-93753). https://kevwire.com/record/CVE-2026-93753

MLA

"deepmerge mergeObject() allows prototype poisoning of returned objects (CVE-2026-93753)." KEVWire, 27 Oct. 2026, kevwire.com/record/CVE-2026-93753.

Chicago

KEVWire. "deepmerge mergeObject() allows prototype poisoning of returned objects (CVE-2026-93753)." Last modified October 27, 2026. https://kevwire.com/record/CVE-2026-93753.

Evidence summary (plain text)

deepmerge mergeObject() allows prototype poisoning of returned objects (Sep 18, 2026).
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.
CVSS 2.7 (version 4.0; evidence as of Oct 27, 2026; https://github.com/advisories/GHSA-gcqx-w48m-w2h4).
Sources:
GitHub-reviewed advisory GHSA-gcqx-w48m-w2h4: https://github.com/advisories/GHSA-gcqx-w48m-w2h4
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-93753.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 23:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

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