CVE-2020-7704: 
JavaScript vulnerability analysis and mitigation

The linux-cmdline package versions before 1.0.1 were identified with a Prototype Pollution vulnerability (CVE-2020-7704). The vulnerability was disclosed on August 14, 2020, and published on August 19, 2020. This security issue affects the package's constructor functionality (Snyk DB).

The vulnerability allows attackers to inject properties into existing JavaScript language construct prototypes through the package's constructor. The issue stems from the ability to manipulate JavaScript object attributes, including magical attributes like proto, constructor, and prototype. When exploited, properties on the Object.prototype are inherited by all JavaScript objects through the prototype chain. The vulnerability has been assigned a CVSS score of 7.5 (High) (CISA Bulletin).

The successful exploitation of this vulnerability can lead to several consequences: denial of service by triggering JavaScript exceptions, tampering with application source code to force specific code paths, and potential remote code execution. The vulnerability can affect the integrity of the application by polluting Object prototypes with unexpected values (Snyk DB).

A proof-of-concept exploit exists demonstrating how the vulnerability can be triggered. The exploit involves using the constructor to inject malicious properties: const linuxCmdline = require('linux-cmdline'); linuxCmdline('__proto__.polluted=true'); console.log(polluted); (Snyk DB).

The vulnerability has been fixed in version 1.0.1 of the linux-cmdline package. Users should upgrade to this version or higher. Additional recommended mitigations include freezing the prototype using Object.freeze(Object.prototype), implementing schema validation for JSON input, avoiding unsafe recursive merge functions, and considering the use of objects without prototypes or using Map instead of Object (Snyk DB).