CVE-2026-54269

protobufjs accepted certain schema-derived names that could collide with properties used by protobufjs runtime helpers. The known affected names are fields named hasOwnProperty, field or oneof names such as $type when loaded through protobufjs JSON/reflection descriptors, and service methods whose generated helper name is rpcCall.

When affected message or service types were used, protobufjs could read schema-controlled data where it expected an own-property helper, reflected type metadata, or the base RPC helper. This could cause deterministic exceptions or recursive calls in affected decode post-checks, verification, object conversion, reflected JSON serialization, or protobufjs RPC helper invocation.

Preconditions

• The application must use an affected protobufjs version.
• The application must load or use a schema or protobufjs JSON descriptor containing one of the problematic names:
  • a field named hasOwnProperty,
  • a field or oneof named $type through protobufjs JSON/reflection descriptor input,
  • or a service method whose generated helper name is rpcCall.
• The application must reach the affected API path for that name: required-field decode post-checks, verify, or toObject for hasOwnProperty; reflected message JSON serialization for $type; or protobufjs RPC service invocation for rpcCall.

Workarounds

Do not load protobuf schemas or protobufjs JSON descriptors from untrusted sources with affected versions. If untrusted schemas or descriptors must be accepted, validate schema-derived field, oneof, and service method names before loading and reject the problematic names described above.

Applications using trusted schemas can avoid the issue by renaming affected fields or service methods, or by avoiding the affected API path.

An attacker who can provide or influence protobuf schemas or protobufjs JSON descriptors may be able to make affected message or service types unusable, resulting in denial of service for the affected processing path.

Applications using only trusted schemas are affected only if those schemas contain one of the problematic names and the application reaches the affected API path.

The issue is not known to allow code execution by itself.

CVE-2026-54269 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. 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 (7.6.3, 2.5.1, 1.3.3, 8.6.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-54269? CVE-2026-54269 is a medium-severity security vulnerability in protobufjs (npm), affecting versions <= 7.6.2. It is fixed in 7.6.3, 2.5.1, 1.3.3, 8.6.0.
2. How severe is CVE-2026-54269? CVE-2026-54269 has a CVSS score of 5.3 (Medium). 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 packages are affected by CVE-2026-54269?
   • protobufjs (npm) (versions <= 7.6.2)
   • protobufjs-cli (npm) (versions >= 2.0.0, <= 2.5.0)
4. Is there a fix for CVE-2026-54269? Yes. CVE-2026-54269 is fixed in 7.6.3, 2.5.1, 1.3.3, 8.6.0. Upgrade to this version or later.
5. Is CVE-2026-54269 exploitable, and should I be worried? Whether CVE-2026-54269 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-2026-54269 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-2026-54269?
   • Upgrade protobufjs to 7.6.3 or later
   • Upgrade protobufjs-cli to 2.5.1 or later
   • Upgrade protobufjs-cli to 1.3.3 or later
   • Upgrade protobufjs to 8.6.0 or later