CVE-2026-59877: protobufjs — Fix

Description

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.

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CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS — Exploit Prediction

0.0037

Probability of exploitation

0.30%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-835 CWE-835

Affected Products

Vendor	Product	Versions
protobufjs_project	protobufjs	< 7.6.5
protobufjs_project	protobufjs	8.0.0 — 8.6.6

References

Advisories & Patches

https://github.com/protobufjs/protobuf.js/commit/10fba6d54815ceecca8a06b9a6db490c8f5d2217 https://github.com/protobufjs/protobuf.js/commit/fa5c73add738ceb471e74da8cc2f3727c3d0a69f https://github.com/protobufjs/protobuf.js/pull/2352 https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-j3f2-48v5-ccww

Other References

https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v7.6.5 https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.6

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-59877? +

CVE-2026-59877 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0037, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-59877? +

CVE-2026-59877 affects products from protobufjs_project, specifically: protobufjs. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-59877? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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