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.
EPSS: 0.004 (29.9th percentile) — read the EPSS interpretation.
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.
Affected products
- Protobufjs Protobuf.js — versions >= 7.5.0, < 7.6.5, >= 8.0.0, < 8.6.6
- Protobufjs_project Protobufjs
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
- security-advisories@github.com (Product, x_refsource_MISC, 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.