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MEDIUM severity

CVE-2021-23700 — merge-deep2

MEDIUM

CVE-2021-23700 is a medium-severity (CVSS 6.5) CWE-1321 vulnerability in merge-deep2. 1 public exploit reference exists, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.

Prototype Pollution in merge-deep2.

Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
1 known
Exploitation data as of Oct 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.2%probability of exploitation in next 30 days
Lower Risk+0.04%
Lower risk than most CVEs67th percentile — riskier than 67% of all scored CVEsHighest risk
0.00%0.57%1.14%1.71%0.5%1.2%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-23700 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

1other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
merge-deep2npm
28downloads / week

Description

All versions of package merge-deep2 are vulnerable to Prototype Pollution via the mergeDeep() function.

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
📦npmmerge-deep2all versionsNo fix

Affected Products

1 product · 1 configurations
Application
merge-deep2merge-deep2_project
all
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

All versions of package merge-deep2 are vulnerable to Prototype Pollutio…

snyk.ioNVDDec 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for merge-deep2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    No patched version of merge-deep2 has shipped for CVE-2021-23700 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  3. Mitigate without a patch

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

All versions of package merge-deep2 are vulnerable to Prototype Pollution via the mergeDeep() function.
O3 Security · Impact-Aware SCA

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CVE-2021-23700: merge-deep2: Prototype Pollution