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Description

protobufjs compiles protobuf definitions into JavaScript (JS) functions. From 8.2.0 until 8.6.5, the protobufjs Text Format extension parsed string-keyed map entries using ordinary property assignment, allowing a map entry with key __proto__ to change the prototype of the returned map object instead of creating an own map entry in protobufjs/ext/textformat. This issue is fixed in version 8.6.5.

PUBLISHED Reserved 2026-07-07 | Published 2026-07-08 | Updated 2026-07-09 | Assigner GitHub_M




MEDIUM: 4.8CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Problem types

CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Product status

>= 8.2.0, < 8.6.5
affected

References

github.com/...buf.js/security/advisories/GHSA-jfj6-75fj-8934

github.com/protobufjs/protobuf.js/pull/2335

github.com/...ommit/9f97fe413072d3beb52c74e62d88ea8adc9444d8

github.com/...fjs/protobuf.js/releases/tag/protobufjs-v8.6.5

cve.org (CVE-2026-59876)

nvd.nist.gov (CVE-2026-59876)

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