Vulnerability in Protobufjs Protobuf.js
CVE-2026-59877
protobufjs compiles protobuf definitions into JavaScript (JS) functions. Prior to 7.6.5 and 8.6.6, protobufjs parsed option names by advancing through schema tokens until reaching an = token without checking for end of input, so a crafted .proto schema that opens an option declaration and ends prematurely can cause parse, Root.load, or Root.loadSync to loop indefinitely. This issue is fixed in versions 7.6.5 and 8.6.6.
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:N/A:L.
EPSS exploit prediction
EPSS: 0.007 (50.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 50.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.007 · change: +0.003
Affected products
- Protobufjs Protobuf.js — versions >= 7.5.0, < 7.6.5, >= 8.0.0, < 8.6.6
- Protobufjs Project
Weakness classification (CWE)
References
- github.com/protobufjs/protobuf.js/security/advisories/GHSA-j3f2-48v5-ccww (Mitigation, Vendor Advisory)
- github.com/protobufjs/protobuf.js/pull/2352 (Patch, Issue Tracking)
- github.com/protobufjs/protobuf.js/commit/10fba6d54815ceecca8a06b9a6db490c8f5d22… (Patch)
- github.com/protobufjs/protobuf.js/commit/fa5c73add738ceb471e74da8cc2f3727c3d0a6… (Patch)
- github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v7.6.5 (Product, Release Notes)
- github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.6 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-59877?
- CVE-2026-59877 is a medium-severity vulnerability in Protobufjs Protobuf.js, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 5.3/10. Published 2026-07-08.
- How severe is CVE-2026-59877?
- Medium severity. CVSS v3 base score is 5.3 out of 10.