protobufjs: Text Format string map parsing can mutate returned map object prototype
Summary
The protobuf.js text format extension parsed string-keyed map entries using ordinary property assignment. A text-format map entry with key __proto__ could therefore change the prototype of the returned map object instead of creating an own map entry.
This affected the optional Text Format extension. Other protobufjs input paths, including binary decode, fromObject, and ProtoJSON conversion, are not affected.
Impact
An attacker who can provide protobuf text-format input parsed by an application using protobufjs/ext/textformat may be able to create message objects whose string-keyed map fields have attacker-controlled prototypes.
This is per-object prototype mutation, not global Object.prototype pollution. Impact depends on downstream application logic treating inherited properties as meaningful, for example by using in, truthiness checks, or direct property access on parsed map objects instead of own-property checks.
Applications that do not parse untrusted Text Format input, or that do not use inherited properties from parsed map objects in security-relevant logic, are not directly affected.
Preconditions
- The application must parse attacker-controlled protobuf Text Format input with
protobufjs/ext/textformat. - The target schema must contain a string-keyed map field.
- The crafted input must provide a map entry with key
__proto__. - Downstream application logic must treat inherited properties on the returned map object as meaningful for impact beyond malformed output.
Workarounds
Upgrade to protobufjs 8.6.5 or newer.
If immediate upgrade is not possible, do not parse untrusted protobuf Text Format input with affected versions. Applications can also reject string map keys named __proto__ before or during Text Format parsing, and should use own-property checks such as Object.hasOwnProperty.call(map, key) when consuming parsed map objects.
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de npm | protobufjs | >= 8.2.0, < 8.6.5 | 8.6.5 |
Referencias
- 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
- https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5
- Vector CVSS
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N- Debilidad (CWE)
CWE-1321- Plataforma
- npm
- Paquete
protobufjs- Publicada
- 20.07.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-jfj6-75fj-8934 - CC BY 4.0
Historial de vulnerabilidades: protobufjs
Todas las vulnerabilidades publicadas de este paquete (Paquete de npm), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 17
- Primera → última
- 10.2018 07.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Crítica 2
- Alta 6
- Media 9
Divulgaciones por año
- 2018: 1
- 2019: 0
- 2020: 0
- 2021: 0
- 2022: 1
- 2023: 1
- 2024: 0
- 2025: 0
- 2026: 14
-
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