CVE-2026-45740

protobufjs could recurse without a depth limit while expanding nested JSON descriptors through Root.fromJSON() and Namespace.addJSON().

A crafted JSON descriptor with deeply nested namespace definitions could cause the JavaScript call stack to be exhausted during descriptor loading.

Preconditions

• The application must load JSON descriptor data influenced by an attacker.
• The crafted descriptor must contain deeply nested nested namespace objects.
• The affected Root.fromJSON() / Namespace.addJSON() descriptor expansion path must process the crafted input.

Workarounds

Avoid loading untrusted protobuf JSON descriptors with affected versions. If immediate upgrade is not possible, reject excessively nested descriptor structures at an outer validation boundary where feasible, or isolate descriptor loading in a process that can be safely restarted.

An attacker who can provide JSON descriptors loaded by an application may be able to crash the process or otherwise cause schema loading to fail with a stack overflow.

This affects applications that load JSON descriptors from untrusted sources with affected versions.

CVE-2026-45740 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 (7.5.8, 8.2.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-45740? CVE-2026-45740 is a medium-severity security vulnerability in protobufjs (npm), affecting versions <= 7.5.7. It is fixed in 7.5.8, 8.2.0.
2. How severe is CVE-2026-45740? CVE-2026-45740 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 versions of protobufjs are affected by CVE-2026-45740? protobufjs (npm) versions <= 7.5.7 is affected.
4. Is there a fix for CVE-2026-45740? Yes. CVE-2026-45740 is fixed in 7.5.8, 8.2.0. Upgrade to this version or later.
5. Is CVE-2026-45740 exploitable, and should I be worried? Whether CVE-2026-45740 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-2026-45740 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-2026-45740?
   • Upgrade protobufjs to 7.5.8 or later
   • Upgrade protobufjs to 8.2.0 or later

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