CVE-2026-54271

A previous fix for unsafe name handling in pbjs static / static-module code generation was incomplete. Affected versions of protobufjs-cli could still emit unsafe JavaScript references when generating static output from crafted JSON descriptor input. The common case of parsing schemas from .proto files is not affected.

This is a bypass of GHSA-6r35-46g8-jcw9 / CVE-2026-44295.

Preconditions

• The application or build process must run pbjs static code generation on a pre-parsed JSON descriptor influenced by an attacker.
• The generated JavaScript file must subsequently be executed or imported.
• An affected generated API path must be invoked.

Workarounds

Do not run affected versions of pbjs static or static-module generation on untrusted JSON descriptors. If untrusted JSON descriptors must be accepted, validate descriptor-derived names before code generation and reject names that could not have been produced by parsing a valid .proto file. Running code generation in an isolated environment can reduce impact.

An attacker who can provide or influence pre-parsed JSON descriptors passed to pbjs static code generation may be able to cause generated JavaScript output to contain attacker-controlled code.

The injected code may execute if the generated file is later executed or imported and an affected generated API path is invoked.

Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.

CVE-2026-54271 has a CVSS score of 8.2 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.3.2, 2.5.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-54271? CVE-2026-54271 is a high-severity code injection vulnerability in protobufjs-cli (npm), affecting versions <= 1.3.1. It is fixed in 1.3.2, 2.5.0. Untrusted input is evaluated as executable code within the application's runtime environment.
2. How severe is CVE-2026-54271? CVE-2026-54271 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of protobufjs-cli are affected by CVE-2026-54271? protobufjs-cli (npm) versions <= 1.3.1 is affected.
4. Is there a fix for CVE-2026-54271? Yes. CVE-2026-54271 is fixed in 1.3.2, 2.5.0. Upgrade to this version or later.
5. Is CVE-2026-54271 exploitable, and should I be worried? Whether CVE-2026-54271 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-54271 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-54271?
   • Upgrade protobufjs-cli to 1.3.2 or later
   • Upgrade protobufjs-cli to 2.5.0 or later