CVE-2026-44292

A flaw was found in protobufjs, a library that compiles protobuf definitions into JavaScript functions. This vulnerability allows an attacker to manipulate the internal structure of message objects. By providing a specially crafted input, an attacker could alter the prototype of individual message instances, potentially leading to unauthorized modification of data or unexpected application behavior, thereby impacting data integrity.

This is an Important vulnerability where protobufjs can be exploited for prototype pollution on individual message instances. Applications that construct protobufjs messages from attacker-controlled plain objects, particularly those parsing untrusted JSON input, are susceptible to data integrity issues through manipulation of the object's prototype chain. This does not affect global prototypes but can lead to unexpected application behavior.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, applications should avoid directly passing attacker-controlled plain objects to protobufjs message constructors. If processing untrusted JSON input, it is crucial to validate or sanitize object keys and explicitly reject any __proto__ properties before constructing protobuf messages. This operational control prevents the manipulation of message instance prototypes.