CVE-2026-59876

protobufjs: Text Format string map parsing can mutate returned map object prototype

Published Jul 8, 2026 CVSS 3.1 · 4.8 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-jfj6-75fj-8934 protobufjs: Text Format string map parsing can mutate returned map object prototype
History
Type Values Removed Values Added
First Time appeared Protobuf
Protobuf protobuf
Vendors & Products Protobuf
Protobuf protobuf
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title protobufjs: Text Format string map parsing can mutate returned map object prototype
Weaknesses CWE-1321
References
Metrics cvssV3_1

{'score': 4.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 9, 2026, 2:41 PM
Reserved
Jul 7, 2026, 3:41 PM
Status
Analyzed
Published
Jul 8, 2026, 4:16 PM
Modified
Oct 25, 2026, 5:10 PM
Severity
Moderate
Public date
Jul 8, 2026, 3:31 PM