CVE-2024-21538 is a high-severity vulnerability affecting the cross-spawn package, specifically versions before 6.0.6 and from 7.0.0 up to but not including 7.0.5. The vulnerability is a Regular Expression Denial of Service (ReDoS) caused by improper input sanitization in the package's handling of input strings. An attacker can exploit this flaw by crafting a specially designed, very large string that triggers excessive CPU consumption during regular expression processing. This leads to resource exhaustion, causing the affected application to slow down significantly or crash entirely. The vulnerability does not require any authentication or user interaction and can be exploited remotely, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The vulnerability is classified under CWE-1333, which relates to ReDoS issues stemming from inefficient regular expression implementations. Although no known exploits are currently reported in the wild, the high CVSS score of 8.7 reflects the potential for impactful denial of service attacks. The cross-spawn package is commonly used in Node.js environments to spawn child processes, often as part of build tools, development utilities, and server-side applications. Therefore, any application or service relying on vulnerable versions of cross-spawn is at risk of being disrupted by this attack vector.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on Node.js-based infrastructure, development pipelines, or server-side applications that incorporate the cross-spawn package. Exploitation can lead to denial of service conditions, resulting in application downtime, degraded performance, and potential disruption of critical business operations. This is particularly concerning for sectors such as finance, healthcare, telecommunications, and government services where availability and reliability are paramount. Additionally, the increased CPU usage caused by the attack could lead to higher operational costs and potential cascading failures in systems with limited resources. Since the vulnerability does not require authentication or user interaction, it can be exploited by remote attackers scanning for vulnerable endpoints, increasing the risk of widespread disruption. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits following public disclosure.

European organizations should take immediate steps to mitigate this vulnerability by upgrading the cross-spawn package to versions 6.0.6 or 7.0.5 and later, where the issue has been addressed. It is critical to audit all Node.js projects and dependencies to identify and update any vulnerable versions of cross-spawn. For environments where immediate upgrading is not feasible, implementing input validation and sanitization to limit the size and complexity of strings processed by cross-spawn can reduce the risk of exploitation. Additionally, deploying runtime protections such as CPU usage monitoring and rate limiting can help detect and mitigate potential ReDoS attacks. Organizations should also consider isolating critical services and applying resource quotas to prevent a single process from exhausting system resources. Regularly monitoring security advisories and integrating automated dependency scanning tools into CI/CD pipelines will help maintain awareness and prompt remediation of similar vulnerabilities in the future.