Prototype Pollution in Jsondiffpatch

CVE-2026-8657

Versions of the package jsondiffpatch before 0.7.6 are vulnerable to Prototype Pollution via the jsondiffpatch.patch() and jsondiffpatch/formatters/jsonpatch.patch() APIs. An attacker can perform prototype pollution by supplying crafted delta or JSON Patch documents, as attacker-controlled property names and path segments are used to traverse and modify objects without restricting access to special properties like __proto__ or constructor.prototype, allowing modification of Object.prototype.

Vulnerability class: Prototype Pollution

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L.

EPSS exploit prediction

EPSS: 0.007 (50.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-8657: held from 0.004 to 0.007.

EPSS over last 30 days · oldest: 0.004 · newest: 0.007 · change: +0.003

Affected products

  • Jsondiffpatch — versions 0
  • Org.webjars.npm:jsondiffpatch — versions 0

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-8657?
CVE-2026-8657 is a high-severity vulnerability in Jsondiffpatch, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 8.2/10. Published 2026-05-16.
How severe is CVE-2026-8657?
High severity. CVSS v3 base score is 8.2 out of 10.