What is CVE-2026-54737?

CVE-2026-54737 is a high-severity security vulnerability in @phun-ky/defaults-deep (npm), affecting versions < 2.0.5. It is fixed in 2.0.5.

How severe is CVE-2026-54737?

CVE-2026-54737 has a CVSS score of 7.3 (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.

Which versions of @phun-ky/defaults-deep are affected by CVE-2026-54737?

@phun-ky/defaults-deep (npm) versions < 2.0.5 is affected.

Is there a fix for CVE-2026-54737?

Yes. CVE-2026-54737 is fixed in 2.0.5. Upgrade to this version or later.

Is CVE-2026-54737 exploitable, and should I be worried?

Whether CVE-2026-54737 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.

What actually determines whether CVE-2026-54737 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.

How do I fix CVE-2026-54737?

Upgrade @phun-ky/defaults-deep to 2.0.5 or later.

CVE-2026-54737 in @phun-ky/defaults-deep

Q: How severe is CVE-2026-54737?

CVE-2026-54737 has a CVSS score of 7.3 (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.

Q: Which versions of @phun-ky/defaults-deep are affected by CVE-2026-54737?

@phun-ky/defaults-deep (npm) versions < 2.0.5 is affected.

Q: Is there a fix for CVE-2026-54737?

Yes. CVE-2026-54737 is fixed in 2.0.5. Upgrade to this version or later.

Q: Is CVE-2026-54737 exploitable, and should I be worried?

Whether CVE-2026-54737 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.

Q: What actually determines whether CVE-2026-54737 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.

Q: How do I fix CVE-2026-54737?

Upgrade @phun-ky/defaults-deep to 2.0.5 or later.

Summary

@phun-ky/defaults-deep Has a Prototype Pollution issue via Unsafe Recursive Property Merging

Workarounds

Users unable to upgrade should ensure that untrusted input is sanitized before being passed to defaultsDeep().

At a minimum, applications should reject or remove the following property names from all levels of user-controlled objects:

__proto__
constructor
prototype

Upgrading to a patched version remains the recommended mitigation.

Impact

A prototype pollution vulnerability exists in @phun-ky/defaults-deep prior to version 2.0.5.

The library recursively merged user-supplied objects without filtering unsafe property names such as __proto__, constructor, and prototype. An attacker able to supply crafted input could cause properties to be written to Object.prototype, resulting in prototype pollution affecting all objects within the running process.

Applications that pass untrusted input to defaultsDeep() may be impacted. Depending on how the application uses merged objects, this could lead to unexpected behavior, logic bypasses, denial of service, or other security issues.

CVE-2026-54737 has a CVSS score of 7.3 (High). 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 (2.0.5); upgrading removes the vulnerable code path.

Affected versions

@phun-ky/defaults-deep (< 2.0.5)

Security releases

@phun-ky/defaults-deep → 2.0.5 (npm)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

This issue has been fixed in version 2.0.5.

Users should upgrade to version 2.0.5 or later.

The fix prevents unsafe prototype-related keys (__proto__, constructor, and prototype) from being processed during recursive merge operations and includes regression tests covering known prototype pollution vectors.

Frequently Asked Questions

What is CVE-2026-54737? CVE-2026-54737 is a high-severity security vulnerability in @phun-ky/defaults-deep (npm), affecting versions < 2.0.5. It is fixed in 2.0.5.
How severe is CVE-2026-54737? CVE-2026-54737 has a CVSS score of 7.3 (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.
Which versions of @phun-ky/defaults-deep are affected by CVE-2026-54737? @phun-ky/defaults-deep (npm) versions < 2.0.5 is affected.
Is there a fix for CVE-2026-54737? Yes. CVE-2026-54737 is fixed in 2.0.5. Upgrade to this version or later.
Is CVE-2026-54737 exploitable, and should I be worried? Whether CVE-2026-54737 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
What actually determines whether CVE-2026-54737 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.
How do I fix CVE-2026-54737? Upgrade @phun-ky/defaults-deep to 2.0.5 or later.