CVE-2025-27209 is a high-severity vulnerability affecting Node.js version 24.0.0, specifically related to the V8 JavaScript engine's string hashing implementation. The vulnerability arises from the re-introduction of a Hash Denial of Service (HashDoS) flaw due to changes in how string hashes are computed using the rapidhash algorithm. An attacker who can control input strings to be hashed can deliberately generate numerous hash collisions, causing excessive computational overhead during hash table operations. Notably, this attack does not require knowledge of the hash seed, lowering the barrier for exploitation. The vulnerability is categorized under CWE-407 (Use of Special Element or Structure), indicating improper handling of hash functions leading to performance degradation. The CVSS v3.0 score is 7.5, reflecting a high severity with network attack vector, low attack complexity, no privileges or user interaction required, and an impact limited to availability (denial of service). Although no known exploits are currently reported in the wild, the vulnerability could be leveraged to disrupt Node.js applications by causing them to consume excessive CPU resources, leading to service outages or degraded performance. Since Node.js is widely used for server-side JavaScript execution, especially in web services and APIs, this vulnerability poses a significant risk to applications relying on string hashing in their workflows.

For European organizations, the impact of CVE-2025-27209 can be substantial, especially for those heavily dependent on Node.js v24.0.0 in production environments. The vulnerability enables remote attackers to cause denial of service conditions without authentication or user interaction, potentially leading to service downtime, degraded user experience, and operational disruptions. Critical sectors such as finance, healthcare, telecommunications, and e-commerce, which often deploy Node.js-based microservices and APIs, may face increased risk of availability loss. This could translate into financial losses, reputational damage, and regulatory scrutiny under frameworks like GDPR if service interruptions affect data processing or customer services. Additionally, the vulnerability could be exploited as part of multi-vector attacks, amplifying the impact on infrastructure resilience. Given the network-based attack vector and ease of exploitation, attackers could launch large-scale automated attacks targeting vulnerable Node.js instances across European organizations.

To mitigate this vulnerability, European organizations should: 1) Immediately identify and inventory all Node.js 24.0.0 deployments within their infrastructure. 2) Apply patches or updates as soon as the Node.js project releases a fix addressing CVE-2025-27209; if no patch is yet available, consider downgrading to a prior stable Node.js version not affected by this issue. 3) Implement input validation and rate limiting on endpoints that accept user-controlled strings to reduce the risk of hash collision attacks. 4) Monitor application performance metrics and logs for unusual CPU spikes or latency increases indicative of hash collision exploitation attempts. 5) Employ Web Application Firewalls (WAFs) or Intrusion Detection Systems (IDS) with signatures or anomaly detection capabilities to detect and block suspicious traffic patterns targeting hash functions. 6) Educate development teams about secure coding practices related to hash function usage and encourage the use of alternative hashing algorithms or libraries that are resistant to collision attacks. 7) Conduct regular security assessments and penetration tests focusing on denial of service vectors in Node.js applications.