PT-2026-56496 · Protobufjs · Protobufjs

Published 2026-07-08 · Updated 2026-07-08 · CVE-2026-59876

Mitre

CVSS v3.1

4.8

Medium

Base vector

AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

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.

Fix

Prototype Pollution

Weakness Enumeration

CWE-1321

Related Identifiers

CVE-2026-59876

Affected Products

Protobufjs

References · 5

• https://nvd.nist.gov/vuln/detail/CVE-2026-59876 · Security Note
• https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5 · Note
• https://github.com/protobufjs/protobuf.js/commit/9f97fe413072d3beb52c74e62d88ea8adc9444d8 · Note
• https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-jfj6-75fj-8934 · Note
• https://github.com/protobufjs/protobuf.js/pull/2335 · Note