CVE-2026-16266

MEDIUMPre-NVD 4.04.0—
EchelonGraph scoreMEDIUM 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 — 3 sources updated this weekElevated
4.0EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 4.0Exploit: Elevated riskExposed: 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(medium)
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 PROB
0%
EPSS %ILE
36%
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 16× in last 7d / 73× 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 135 total refreshes for this CVE.

  1. 2026-09-11 14:52 UTCEPSS rescore
  2. 2026-09-11 09:36 UTCEPSS rescore
  3. 2026-09-11 09:16 UTCEG score recompute
  4. 2026-09-11 09:16 UTCGHSA enrichment
  5. 2026-09-10 09:34 UTCEPSS rescore
  6. 2026-09-09 11:42 UTCEG score recompute
  7. 2026-09-09 11:42 UTCGHSA enrichment
  8. 2026-09-08 22:00 UTCEPSS rescore
  9. 2026-09-07 22:45 UTCEG score recompute
  10. 2026-09-07 22:45 UTCGHSA enrichment
  11. 2026-09-07 16:01 UTCEPSS rescore
  12. 2026-09-06 13:47 UTCEPSS rescore
  13. 2026-09-06 11:21 UTCEG score recompute
  14. 2026-09-06 11:21 UTCGHSA enrichment
  15. 2026-09-05 09:15 UTCEG score recompute
  16. 2026-09-05 09:15 UTCGHSA enrichment
  17. 2026-09-04 05:06 UTCEPSS rescore
  18. 2026-09-02 14:11 UTCEPSS rescore
  19. 2026-09-02 01:00 UTCEG score recompute
  20. 2026-09-02 01:00 UTCGHSA enrichment
  21. 2026-09-01 13:53 UTCEPSS rescore
  22. 2026-09-01 04:39 UTCEPSS rescore
  23. 2026-08-31 02:07 UTCEG score recompute
  24. 2026-08-31 02:07 UTCGHSA enrichment
  25. 2026-08-30 19:17 UTCEPSS rescore
Show 75 more
  1. 2026-08-30 02:25 UTCEG score recompute
  2. 2026-08-30 02:25 UTCGHSA enrichment
  3. 2026-08-30 01:22 UTCEPSS rescore
  4. 2026-08-28 21:41 UTCEPSS rescore
  5. 2026-08-27 22:02 UTCEG score recompute
  6. 2026-08-27 22:02 UTCGHSA enrichment
  7. 2026-08-27 14:25 UTCEPSS rescore
  8. 2026-08-26 22:20 UTCEG score recompute
  9. 2026-08-26 22:20 UTCGHSA enrichment
  10. 2026-08-26 14:46 UTCEPSS rescore
  11. 2026-08-25 22:38 UTCEG score recompute
  12. 2026-08-25 22:38 UTCGHSA enrichment
  13. 2026-08-25 13:48 UTCEPSS rescore
  14. 2026-08-24 21:42 UTCEG score recompute
  15. 2026-08-24 21:42 UTCGHSA enrichment
  16. 2026-08-23 21:40 UTCEG score recompute
  17. 2026-08-23 21:40 UTCGHSA enrichment
  18. 2026-08-23 00:19 UTCEPSS rescore
  19. 2026-08-22 21:59 UTCEG score recompute
  20. 2026-08-22 21:59 UTCGHSA enrichment
  21. 2026-08-21 23:49 UTCEPSS rescore
  22. 2026-08-21 22:17 UTCEG score recompute
  23. 2026-08-21 22:17 UTCGHSA enrichment
  24. 2026-08-20 22:55 UTCEPSS rescore
  25. 2026-08-20 22:27 UTCEG score recompute
  26. 2026-08-20 22:27 UTCGHSA enrichment
  27. 2026-08-19 22:45 UTCEG score recompute
  28. 2026-08-19 22:45 UTCGHSA enrichment
  29. 2026-08-19 17:03 UTCEPSS rescore
  30. 2026-08-18 21:49 UTCEG score recompute
  31. 2026-08-18 21:48 UTCGHSA enrichment
  32. 2026-08-18 13:48 UTCEPSS rescore
  33. 2026-08-17 21:52 UTCEG score recompute
  34. 2026-08-17 21:52 UTCGHSA enrichment
  35. 2026-08-17 13:47 UTCEPSS rescore
  36. 2026-08-16 21:58 UTCEG score recompute
  37. 2026-08-16 21:58 UTCGHSA enrichment
  38. 2026-08-16 14:56 UTCEPSS rescore
  39. 2026-08-16 02:14 UTCEPSS rescore
  40. 2026-08-15 22:16 UTCEG score recompute
  41. 2026-08-15 22:16 UTCGHSA enrichment
  42. 2026-08-15 01:30 UTCEPSS rescore
  43. 2026-08-14 22:33 UTCGHSA enrichment
  44. 2026-08-13 22:51 UTCEG score recompute
  45. 2026-08-13 22:51 UTCGHSA enrichment
  46. 2026-08-13 22:00 UTCEPSS rescore
  47. 2026-08-12 23:09 UTCEG score recompute
  48. 2026-08-12 23:09 UTCGHSA enrichment
  49. 2026-08-12 13:50 UTCEPSS rescore
  50. 2026-08-11 23:27 UTCEG score recompute
  51. 2026-08-11 23:27 UTCGHSA enrichment
  52. 2026-08-11 13:42 UTCEPSS rescore
  53. 2026-08-11 00:00 UTCEPSS rescore
  54. 2026-08-10 23:46 UTCGHSA enrichment
  55. 2026-08-10 00:04 UTCEG score recompute
  56. 2026-08-10 00:04 UTCGHSA enrichment
  57. 2026-08-09 13:46 UTCEPSS rescore
  58. 2026-08-09 00:23 UTCEG score recompute
  59. 2026-08-09 00:23 UTCGHSA enrichment
  60. 2026-08-08 16:37 UTCEPSS rescore
  61. 2026-08-08 00:41 UTCEG score recompute
  62. 2026-08-08 00:41 UTCGHSA enrichment
  63. 2026-08-07 00:59 UTCEG score recompute
  64. 2026-08-07 00:59 UTCGHSA enrichment
  65. 2026-08-06 13:46 UTCEPSS rescore
  66. 2026-08-06 01:18 UTCEG score recompute
  67. 2026-08-06 01:18 UTCGHSA enrichment
  68. 2026-08-05 19:17 UTCEPSS rescore
  69. 2026-08-05 01:36 UTCEG score recompute
  70. 2026-08-05 01:36 UTCGHSA enrichment
  71. 2026-08-04 15:10 UTCEPSS rescore
  72. 2026-08-04 10:38 UTCEPSS rescore
  73. 2026-08-04 01:55 UTCEG score recompute
  74. 2026-08-04 01:55 UTCGHSA enrichment
  75. 2026-08-03 10:35 UTCEPSS rescore

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 0% probability of exploitation in the next 30 days, which ranks it in the top 64.2% of all scored CVEs.
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

Explore →

Is Your Infrastructure Affected by CVE-2026-16266?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs