🛡️ CVE-2026-54737 — defaults-deep

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-1321 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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.

Patches

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.

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity low, availability low.

Weakness class

CVE-2026-54737 is classified as CWE-1321: Prototype Pollution. Attacker input can modify an object prototype, changing behaviour for objects across the application.

Affected software

CVE-2026-54737 is recorded against 2 packages.

  • @phun-ky/defaults-deep
  • unknown

Timeline and source

Published on 31 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
github.com (Web)
github.com (Web)
github.com (Package)
github.com (Web)

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
CWE CWE-1321
Public Exploit ✅ No
Source NVD
Published 2026-07-31
Updated 2026-08-12
Modified 2026-07-31
Fix URL N/A

Affected Packages

Software From version Fixed in
@phun-ky/defaults-deep — —
unknown — —

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