CVE-2025-5889 identifies a regular expression denial of service (ReDoS) vulnerability in the juliangruber brace-expansion npm package that enables attackers to cause service disruption through inefficient regular expression complexity in the expand function processing. This vulnerability affects brace-expansion versions 1.1.0 through 1.1.11, 2.0.0 through 2.0.1, 3.0.0, and 4.0.0, achieving a CVSS score of 3.1 (Low severity) with EPSS percentile of 16.1 indicating moderate exploit risk for Node.js applications that utilize brace expansion functionality for shell-style pattern matching. The vulnerability details reveal that improper regular expression patterns in the expand function allow attackers to craft malicious input strings that trigger exponential backtracking behavior, creating substantial exploit risk for applications processing user-controlled brace expansion patterns and affecting application availability without impacting data confidentiality or integrity. The root cause analysis reveals that the vulnerability stems from an inefficient regular expression pattern /,.}/ in the expand function that enables catastrophic backtracking attacks, classified as CWE-400 (Uncontrolled Resource Consumption) and CWE-1333 (Inefficient Regular Expression Complexity). The vulnerability specifically affects regular expression processing where the original pattern allowed for excessive computational complexity when parsing specially crafted brace expansion patterns, enabling attackers to trigger known exploited vulnerabilities through malformed input. Mitigation steps require upgrading to patched brace-expansion versions 1.1.12, 2.0.2, 3.0.1, or 4.0.1 which implement optimized regular expression patterns /,(?!,).}/ that prevent catastrophic backtracking while maintaining functional equivalence. Organizations should prioritize identifying Node.js applications using vulnerable brace-expansion versions, implement input validation and rate limiting for pattern processing functionality, monitor CPU usage patterns for ReDoS attack indicators, and maintain updated vulnerability database records to track similar regular expression complexity vulnerabilities that could compromise application availability through resource exhaustion attacks in JavaScript pattern matching libraries and broader security implications for applications processing untrusted user input patterns.