CVE-2026-54270 protobufjs: Memory amplification from preserved unknown fields in binary decode
Attackers can cause memory exhaustion and denial of service by sending crafted protobuf payloads with many unknown fields to applications using vulnerable protobufjs versions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54270?
CVE-2026-54270 is a medium-severity denial of service vulnerability in protobufjs protobuf.js, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
protobufjs compiles protobuf definitions into JavaScript (JS) functions. From 8.2.0 to 8.4.2, protobufjs 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.
Weakness: CWE-770
Which versions are affected by CVE-2026-54270?
2 open source packages ship an affected version, including protobufjs. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
protobufjs npm | From 8.2.0 | 8.5.0 |
protobufjs npm | From 8.2.0 | 8.5.0 |
Products include Protobufjs Project Protobufjs.
How do I fix CVE-2026-54270?
Upgrade protobufjs to 8.5.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-54270 being exploited?
There is no known exploitation of CVE-2026-54270 in the wild and no public exploit code.
Other vulnerabilities in protobufjs protobuf.js
- CVE-2023-36665 protobufjs Prototype Pollution vulnerability
- CVE-2026-41242 protobufjs has an arbitrary code execution issue
- CVE-2022-25878 Prototype Pollution
- CVE-2026-44291 protobufjs: Code generation gadget after prototype pollution
- CVE-2026-44293 protobufjs: Code injection through bytes field defaults in generated toObject code
Sources
Also known as GHSA-94rc-8x27-4472, MINI-623v-wj9h-7mpw, ROOT-APP-NPM-CVE-2026-54270.