CVE-2021-23518: 
JavaScript vulnerability analysis and mitigation

The cached-path-relative package versions before 1.1.0 contain a Prototype Pollution vulnerability (CVE-2021-23518). The vulnerability exists in the cachedPathRelative function where the cache variable is set as {} instead of Object.create(null), allowing access to parent prototype properties when the object is used to create the cached relative path. This vulnerability is particularly notable as it stems from an incomplete fix of a previous security issue (Snyk Advisory).

The vulnerability occurs when using the origin path as proto, causing the attribute of the object to be accessed instead of a path. The issue has received a CVSS v3.1 Base Score of 9.8 (CRITICAL) from NVD and 7.3 (HIGH) from Snyk. The vulnerability is classified under CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes) (NVD).

When exploited, this Prototype Pollution vulnerability can lead to denial of service by triggering JavaScript exceptions or potentially enable code path manipulation leading to remote code execution. The attacker can manipulate object prototype attributes to overwrite or pollute JavaScript application object prototypes (Snyk Advisory).

The vulnerability has been fixed in version 1.1.0 of the cached-path-relative package. The fix involves using Object.create(null) instead of {} for cache initialization. Users should upgrade to version 1.1.0 or higher to address this security issue (GitHub Patch).

The vulnerability has been acknowledged and addressed by multiple organizations. Debian included this fix in their security updates (DLA 3221-1), demonstrating the widespread impact of this security issue (Debian Advisory).