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

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Summary

CVECVE-2026-59876
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-08 16:16:34 UTC
Updated2026-07-08 16:16:34 UTC
Descriptionprotobufjs 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.

Risk And Classification

Primary CVSS: v3.1 4.8 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Problem Types: CWE-1321 | CWE-1321 CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
3.1CNADECLARED4.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Protobufjs Protobuf.js affected >= 8.2.0, < 8.6.5 Not specified

References

ReferenceSourceLinkTags
github.com/protobufjs/protobuf.js/pull/2335 [email protected] github.com
github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5 [email protected] github.com
github.com/protobufjs/protobuf.js/security/advisories/GHSA-jfj6-75fj-8934 [email protected] github.com
github.com/protobufjs/protobuf.js/commit/9f97fe413072d3beb52c74e62d88ea8... [email protected] github.com
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