CVE-2026-59876
protobufjs: Text Format string map parsing can mutate returned map object prototype
CVSS Score
4.8
EPSS Score
0.2%
EPSS Percentile
13th
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.
| CWE | CWE-1321 |
| Vendor | protobufjs |
| Product | protobuf.js |
| Published | Jul 8, 2026 |
| Last Updated | Jul 9, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None
Affected Versions
protobufjs / protobuf.js
>= 8.2.0, < 8.6.5
References
github.com: https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-jfj6-75fj-8934 github.com: https://github.com/protobufjs/protobuf.js/pull/2335 github.com: https://github.com/protobufjs/protobuf.js/commit/9f97fe413072d3beb52c74e62d88ea8adc9444d8 github.com: https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5