Prototype Pollution in Protobufjs Protobuf.js
CVE-2026-44292
protobufjs compiles protobuf definitions into JavaScript (JS) functions. Prior to 7.5.6 and 8.0.2, 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. This vulnerability is fixed in 7.5.6 and 8.0.2.
Vulnerability class: Prototype Pollution
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (25.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 25.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.001
Affected products
- Protobufjs Protobuf.js — versions < 7.5.6, >= 8.0.0, < 8.0.2
- Protobufjs Project
Weakness classification (CWE)
References
- github.com/protobufjs/protobuf.js/security/advisories/GHSA-fx83-v9x8-x52w (Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-44292?
- CVE-2026-44292 is a medium-severity vulnerability in Protobufjs Protobuf.js, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 5.3/10. Published 2026-05-13.
- How severe is CVE-2026-44292?
- Medium severity. CVSS v3 base score is 5.3 out of 10.