CVE-2025-53603 is a high-severity vulnerability identified in Alinto SOPE's SOGo product versions 2.0.2 through 5.12.2. The issue stems from a NULL pointer dereference in the sope-core component, specifically within the NGExtensions/NGHashMap.m module. This vulnerability is triggered when a specially crafted request contains a query string parameter that duplicates a parameter in the POST body. The software fails to properly handle this condition, leading to a NULL pointer dereference and causing the SOGo service to crash. This denial-of-service (DoS) condition can be exploited remotely without any authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The vulnerability impacts availability but does not affect confidentiality or integrity. Although no known exploits are currently reported in the wild, the ease of exploitation and the direct impact on service availability make this a significant risk for organizations relying on Alinto SOPE SOGo for email and groupware services. The lack of a patch at the time of publication further increases the urgency for mitigation.

For European organizations, the impact of CVE-2025-53603 could be substantial, particularly for entities that depend on Alinto SOPE SOGo for critical communication and collaboration infrastructure. A successful exploitation results in a denial-of-service condition, disrupting email and groupware availability, which can hinder business operations, internal communications, and customer interactions. This disruption could affect sectors such as government agencies, financial institutions, healthcare providers, and large enterprises where continuous availability of messaging services is essential. Additionally, prolonged outages could lead to reputational damage and potential regulatory scrutiny under frameworks like GDPR if service disruptions affect data processing or availability commitments. Given the vulnerability requires no authentication, attackers can easily target exposed SOGo instances over the network, increasing the risk of widespread disruption.

Organizations should immediately audit their environments to identify any deployments of Alinto SOPE SOGo versions 2.0.2 through 5.12.2. Until an official patch is released, the following mitigations are recommended: 1) Implement network-level protections such as Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) configured to detect and block requests with duplicate parameters in query strings and POST bodies. 2) Restrict external access to SOGo services to trusted IP ranges or VPN-only access to reduce exposure. 3) Monitor logs for unusual request patterns indicative of exploitation attempts, focusing on malformed or duplicate parameter requests. 4) Engage with Alinto support for any available patches or workarounds and plan for prompt application once available. 5) Consider deploying rate limiting on the affected endpoints to mitigate potential DoS attempts. 6) Prepare incident response plans to quickly restore service availability in case of an attack.