protobufjs: Denial of Service via infinite loop in .proto option parsing

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-59877: 0.36% estimated exploitation activity in the next 30 days; percentile 30.45 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

20 Jul 2026, 22:03 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:57 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-j3f2-48v5-ccww

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-j3f2-48v5-ccww

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# Patch Next advisory brief: CVE-2026-59877

Advisory: protobufjs: Denial of Service via infinite loop in .proto option parsing
IDs: CVE-2026-59877, GHSA-j3f2-48v5-ccww
Record: https://patchnext.com/advisories/cve-2026-59877 (revision 2, source checked 26 Oct 2026, 12:57 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: protobufjs 8.6.6, 7.6.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm protobufjs: affected >= 7.5.0, <= 7.6.4; >= 8.0.0, <= 8.6.5; fixed in 7.6.5, 8.6.6

## Suggested inspection (read-only)
- `npm ls protobufjs --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on protobufjs.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-j3f2-48v5-ccww (OSV record GHSA-j3f2-48v5-ccww lists affected ranges: npm protobufjs >=7.5.0 =8.0.0 <8.6.6 (fixed))
- Verified: https://github.com/advisories/GHSA-j3f2-48v5-ccww (GitHub-reviewed advisory GHSA-j3f2-48v5-ccww lists affected ranges: npm protobufjs >=7.5.0 =8.0.0 <=8.6.5)

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