CVE-2026-59876
Medium
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.
SeverityMedium
CVSS4.8
Exploit probability—
ProductProtobufjs
PublishedJul 8, 2026
First seenJul 8, 2026
Weakness typeCWE-1321Prototype pollution
How to fix
Update
- protobufjs_project protobufjs8.6.5 or later
- protobufjs8.6.5 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| protobufjs_project protobufjs | 8.2.0 ≤ v < 8.6.5 | 8.6.5 |
| protobufjsnpm | 8.2.0 ≤ v < 8.6.5 | 8.6.5 |
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