CVE-2026-59876mediumCWE-1321

CVE-2026-59876: medium-severity vulnerability in protobufjs protobuf.js

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

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 4.8epss 0.3%
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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Affected products
protobufjs · protobuf.js
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