protobuf.js: Prototype injection in generated message constructors

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:L/A:N

EPSS

• CVE-2026-44292: 0.26% estimated exploitation activity in the next 30 days; percentile 18.35 (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 generated message constructors copied enumerable properties from a provided properties object without filtering the proto key. If an application constructed a message from an attacker-controlled plain object, an own enumerable proto property could alter the prototype of that individual message instance. Impact An attacker who can control the properties object passed to a generated protobufjs message constructor or creation helper may be able to modify the prototype chain of the resulting message instance. This is a per-instance prototype injection issue. It does not pollute Object.prototype or other global prototypes. The impact depends on downstream application behavior, such as relying on inherited properties, prototype methods, or instanceof checks for message objects. Applications that only decode binary protobuf data, or that construct messages from trusted application-defined objects, are not directly affected by this issue. Preconditions - The application…

Published by the source

12 May 2026, 15:01 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:52 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-fx83-v9x8-x52w

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-fx83-v9x8-x52w

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-44292

Advisory: protobuf.js: Prototype injection in generated message constructors
IDs: CVE-2026-44292, GHSA-fx83-v9x8-x52w
Record: https://patchnext.com/advisories/cve-2026-44292 (revision 2, source checked 26 Oct 2026, 12:52 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 8.0.2, 7.5.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm protobufjs: affected <= 7.5.5; >= 8.0.0, <= 8.0.1; fixed in 7.5.6, 8.0.2

## 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-fx83-v9x8-x52w (OSV record GHSA-fx83-v9x8-x52w lists affected ranges: npm protobufjs >=0 =8.0.0 <8.0.2 (fixed))
- Verified: https://github.com/advisories/GHSA-fx83-v9x8-x52w (GitHub-reviewed advisory GHSA-fx83-v9x8-x52w lists affected ranges: npm protobufjs >=0 =8.0.0 <=8.0.1)

Commands are suggestions: review each one before running it.