medium4.8
CVE-2026-59876
protobufjs: Text Format string map parsing can mutate returned map object prototype
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | protobufjs | >= 8.2.0, <= 8.6.4 | 8.6.5 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Protobufjs Project | Protobufjs | from 8.2.0 before 8.6.5 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-jfj6-75fj-8934
- https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-jfj6-75fj-8934
- https://nvd.nist.gov/vuln/detail/CVE-2026-59876
- https://github.com/protobufjs/protobuf.js/pull/2335
- https://github.com/protobufjs/protobuf.js/commit/9f97fe413072d3beb52c74e62d88ea8adc9444d8
- https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5