CVE-2026-44292

protobufjs generated message constructors copied enumerable properties from a provided properties object without filtering the __proto__ key. If an application constructed a message from an attacker-controlled plain object, an own enumerable __proto__ property could alter the prototype of that individual message instance.

Preconditions

• The application must allow an attacker to control or influence a plain object used to construct a protobufjs message.
• The object must contain an own enumerable __proto__ property, for example from parsed JSON input.
• The application must pass that object to a generated message constructor or creation helper that copies arbitrary enumerable properties.

Workarounds

Do not pass attacker-controlled plain objects directly to generated message constructors with affected versions. If untrusted JSON input must be accepted, validate or sanitize object keys before constructing messages, and reject __proto__ properties.

An attacker who can control the properties object passed to a generated protobufjs message constructor or creation helper may be able to modify the prototype chain of the resulting message instance.

This is a per-instance prototype injection issue. It does not pollute Object.prototype or other global prototypes. The impact depends on downstream application behavior, such as relying on inherited properties, prototype methods, or instanceof checks for message objects.

Applications that only decode binary protobuf data, or that construct messages from trusted application-defined objects, are not directly affected by this issue.

CVE-2026-44292 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (7.5.6, 8.0.2); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44292? CVE-2026-44292 is a medium-severity security vulnerability in protobufjs (npm), affecting versions <= 7.5.5. It is fixed in 7.5.6, 8.0.2.
2. How severe is CVE-2026-44292? CVE-2026-44292 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of protobufjs are affected by CVE-2026-44292? protobufjs (npm) versions <= 7.5.5 is affected.
4. Is there a fix for CVE-2026-44292? Yes. CVE-2026-44292 is fixed in 7.5.6, 8.0.2. Upgrade to this version or later.
5. Is CVE-2026-44292 exploitable, and should I be worried? Whether CVE-2026-44292 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44292 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44292?
   • Upgrade protobufjs to 7.5.6 or later
   • Upgrade protobufjs to 8.0.2 or later