CVE-2021-26707

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 1.9%, top 22% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 2%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

The merge-deep library before 3.0.3 for Node.js can be tricked into overwriting properties of Object.prototype or adding new properties to it. These properties are then inherited by every object in the program, thus facilitating prototype-pollution attacks against applications using this library.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
—
EPSS
77.5%
KEV
Not listed

Published

June 2, 2021

Last Modified

November 21, 2024

Advisory Details (3)

Auto-updated Jun 13, 2026
Upstream fix merged — awaiting tagged release. Sources: github, github_commit.
github

GHSL-2020-160: Prototype pollution in Merge-deep | GitHub Security Lab

https://securitylab.github.com/advisories/GHSL-2020-160-merge-deep/
generic

NetApp Product Security

https://security.netapp.com/advisory/ntap-20210716-0008/
github_commit

commit 11e5dd56de8a (jonschlinkert/merge-deep)

Fix landed in jonschlinkert/merge-deep commit 11e5dd56de8a — awaiting tagged release

https://github.com/jonschlinkert/merge-deep/commit/11e5dd56de8a6aed0b1ed022089dbce6968d82a5

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
merge-deep—3.0.3—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 101 total refreshes for this CVE.

  1. 2026-07-22 22:45 UTCEG score recompute
  2. 2026-07-22 14:06 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2021-26707?
CVE-2021-26707 is a critical vulnerability published on June 2, 2021. The merge-deep library before 3.0.3 for Node.js can be tricked into overwriting properties of Object.prototype or adding new properties to it. These properties are then inherited by every object in the program, thus facilitating prototype-pollution attacks against applications using this library.
When was CVE-2021-26707 disclosed?
CVE-2021-26707 was first published in the National Vulnerability Database on June 2, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-26707 actively exploited?
CVE-2021-26707 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 77.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-26707?
CVE-2021-26707 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-26707?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-26707, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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