protobufjs: Denial of Service via infinite loop in .proto option parsing
## Summary protobufjs parsed option names by advancing through schema tokens until it reached an `=` token, without checking for end of input. A crafted `.proto` schema that opens an option declaration but ends prematurely could cause the option parser to loop without ever terminating. This affects the reflection parsing path (`parse`, `Root.load`, `Root.loadSync`). ## Impact An attacker who can provide or influence `.proto` schema text parsed by an application may be able to cause the parsing call to never return. Because Node.js is single-threaded, the blocked event loop prevents all other work in the process, resulting in a denial of service that persists until the process is externally terminated. Applications that only encode or decode protobuf binary data with trusted schemas are not directly affected. ## Preconditions - The application must parse `.proto` schema text influenced by an attacker. - The schema must be parsed through APIs such as `parse`, `Root.load`, or `Root.loadSync`. - The crafted input must begin an option declaration that ends before its `=` assignment. ## Workarounds Do not parse `.proto` schemas from untrusted sources with affected versions. If untrusted schema text must be accepted, isolate parsing in a process or worker that can be safely terminated and bound it with a timeout, so a non-returning parse call cannot deny service to the rest of the application.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-59877US | high7.5 | — | ||
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… | ||||
references
External citations — patches, advisories, analysis.
- https://github.com/protobufjs/protobuf.jsPACKAGE
- https://github.com/protobufjs/protobuf.js/commit/10fba6d54815ceecca8a06b9a6db490c8f5d2217WEB
- https://github.com/protobufjs/protobuf.js/commit/fa5c73add738ceb471e74da8cc2f3727c3d0a69fWEB
- https://github.com/protobufjs/protobuf.js/pull/2352WEB
- https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v7.6.5WEB
- https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.6WEB
- https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-j3f2-48v5-ccwwWEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-59877ADVISORY
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