protobufjs: Memory amplification from preserved unknown fields in binary decode

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-2026-54270: 0.40% estimated exploitation activity in the next 30 days; percentile 34.52 (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 8.2.0 added support for preserving unknown fields encountered during binary decode. Affected versions preserved unknown wire elements in message.$unknowns and did not provide a decode-time option to discard unknown fields before retaining them. A crafted protobuf payload containing many unknown fields could therefore cause a decoded message to retain substantially more memory than the input size would suggest, even when unknown-field round-tripping is not needed. protobufjs 8.5.0 added the relevant decode-time options, allowing applications that decode untrusted protobuf data to disable unknown-field retention during decode. protobufjs 8.6.2 flips the default so unknown fields are discarded unless explicitly opted into. Impact An attacker who can provide protobuf binary data decoded by an application using affected protobufjs versions may be able to increase memory pressure by sending messages with many unknown fields. This can degrade availability or contribute to…

Published by the source

15 Jun 2026, 20:13 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-94rc-8x27-4472

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-94rc-8x27-4472

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# Patch Next advisory brief: CVE-2026-54270

Advisory: protobufjs: Memory amplification from preserved unknown fields in binary decode
IDs: CVE-2026-54270, GHSA-94rc-8x27-4472
Record: https://patchnext.com/advisories/cve-2026-54270 (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 8.5.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm protobufjs: affected >= 8.2.0, <= 8.4.2; fixed in 8.5.0

## 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-94rc-8x27-4472 (OSV record GHSA-94rc-8x27-4472 lists affected ranges: npm protobufjs >=8.2.0 <8.5.0 (fixed))
- Verified: https://github.com/advisories/GHSA-94rc-8x27-4472 (GitHub-reviewed advisory GHSA-94rc-8x27-4472 lists affected ranges: npm protobufjs >=8.2.0 <=8.4.2)

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