CVE-2026-16266

MEDIUMPre-NVD 4.04.0—
EchelonGraph scoreHIGH confidence

Score 4.0 from GitHub Security Advisory published 2026-07-21. a secondary CVSS source baseline 4.0; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this weekElevated
4.0
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 4.0Exploit: NoneExposed: 0

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

Versions of the package mongo-object before 3.0.3 are vulnerable to Prototype Pollution via the expandKey() function in util.js. An attacker can modify the JavaScript prototype chain by supplying a crafted property path containing special keys such as __proto__.

CVSS v3
4.0
EG Score
4.0(high)
EG Risk
34(Track)
EG Risk 34/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity40% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
16.1%
KEV
Not listed

Published

July 21, 2026

Last Modified

July 23, 2026

Advisory Details (3)

Auto-updated Jul 21, 2026
Patch available. Sources: github_commit.
generic

Prototype Pollution in mongo-object | CVE-2026-16266 | Snyk

https://security.snyk.io/vuln/SNYK-JS-MONGOOBJECT-13816714
generic

Prototype Pollution in expandKey function · Issue #27 · longshotlabs/mongo-object · GitHub

https://github.com/longshotlabs/mongo-object/issues/27
github_commit Patch Available

commit 638314107d8b (longshotlabs/mongo-object)

Patch available: longshotlabs/mongo-object 3.0.3 (contains commit 638314107d8b)

https://github.com/longshotlabs/mongo-object/commit/638314107d8b397e5453c28e41729522b3e8d67c

Vendor Advisories for CVE-2026-16266(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 10× 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.

  1. 2026-07-23 14:18 UTCEPSS rescore
  2. 2026-07-23 03:05 UTCEG score recompute
  3. 2026-07-22 23:23 UTCEG score recompute
  4. 2026-07-22 23:23 UTCGHSA enrichment
  5. 2026-07-22 14:08 UTCEPSS rescore
  6. 2026-07-21 15:24 UTCEPSS rescore
  7. 2026-07-21 06:49 UTCEG score recompute
  8. 2026-07-21 06:49 UTCGHSA enrichment
  9. 2026-07-21 05:44 UTCEG score recompute
  10. 2026-07-21 05:43 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-16266?
CVE-2026-16266 is a medium vulnerability published on July 21, 2026. Versions of the package mongo-object before 3.0.3 are vulnerable to Prototype Pollution via the expandKey() function in util.js. An attacker can modify the JavaScript prototype chain by supplying a crafted property path containing special keys such as proto.
When was CVE-2026-16266 disclosed?
CVE-2026-16266 was first published in the National Vulnerability Database on July 21, 2026, with the most recent update on July 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-16266 actively exploited?
CVE-2026-16266 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 16.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-16266?
CVE-2026-16266 has a CVSS v3 base score of 4.0 (NVD).
How do I remediate CVE-2026-16266?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-16266, 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.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-16266

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