CVE-2021-25944: 
JavaScript vulnerability analysis and mitigation

Prototype pollution vulnerability in 'deep-defaults' package versions 1.0.0 through 1.0.5 was discovered and disclosed on May 25, 2021. The vulnerability affects Node.js applications using the affected versions of the deep-defaults package (WhiteSource DB).

The vulnerability exists in the _deepDefaults() function which fails to validate object types before property assignment. The function accepts dest and src as arguments but lacks validation on the values passed into the src argument. This allows attackers to supply malicious values by including the __proto__ property. Without proper validation of whether the assigned argument is the Object's own property, properties can be directly assigned to new objects, leading to Object prototype pollution (WhiteSource DB). The vulnerability has been assigned a CVSS v3.1 base score of 9.8 CRITICAL (Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) (NVD).

The vulnerability can be exploited to cause denial of service conditions and potentially achieve remote code execution. When exploited, attackers can create non-existent properties or manipulate existing properties in the Object prototype (WhiteSource DB).

Several mitigation strategies are recommended: 1) Freeze objects to prevent adding, removing, or changing properties, 2) Implement JSON input validation with schema validation to ensure only predefined attributes are allowed, 3) Use Object.create to create objects without prototype association. However, no fixed version is currently available (WhiteSource DB).