CVE-2026-54270: protobufjs memory amplification via unknown field preservation

CVE-2026-54270 · Severity: medium · CVSS 5.3 · Published 2026-06-22

A vulnerability in the protobufjs library, which is used to handle data communication in JavaScript applications, could allow an attacker to cause a service to consume excessive amounts of memory. By sending specially crafted messages containing many "unknown" data fields, an attacker can force the application to store significantly more data than expected. This can lead to slowed performance, service crashes, or system instability, potentially disrupting business operations.

Technologies: protobufjs (npm). Vendors: npm.

Quick answers

Is CVE-2026-54270 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-54270 being exploited in the wild.
How severe is CVE-2026-54270?
Medium severity, with a CVSS score of 5.3, published 22 June 2026.
Which products and versions are affected?
protobufjs (npm) >= 8.2.0, <= 8.4.2, SEMVER:introduced=8.2.0,fixed=8.5.0.
Is there a fix for CVE-2026-54270?
Yes. protobufjs (npm): upgrade to 8.5.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-54270 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-54270?
Check whether you run protobufjs (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • protobufjs (npm): upgrade to 8.5.0 or later
    npm install protobufjs@8.5.0

Technical details

The vulnerability is classified as CWE-770 (Allocation of Resources Without Limits or Throttling). Between versions 8.2.0 and 8.4.2, protobufjs automatically preserved unknown wire elements in the 'message.$unknowns' property without providing a mechanism to discard them during the decoding process. An attacker can exploit this by sending a crafted protobuf payload with a high density of unknown fields, causing the decoded object to occupy substantially more memory than the original input size. This is a network-reachable attack requiring no authentication. The issue was addressed in version 8.5.0 by adding 'discardUnknown' options, and version 8.6.2 changed the default behavior to discard unknown fields unless explicitly opted in.

Affected products

  • protobufjs protobuf.js >=8.2.0, < 8.5.0

Identifiers

  • CVE-2026-54270
  • GHSA-94rc-8x27-4472

Timeline

  • 2026-06-12: advisory: GitHub Security Advisory published
  • 2026-06-22: disclosed: NVD publication date

References

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