CVE-2025-61258 is a denial of service (DoS) vulnerability identified in the Outsystems Platform Server version 11.18.1.37828. The vulnerability is triggered by sending an HTTP request with a crafted Content-Length header that does not match the actual length of the HTTP body. This mismatch causes the server to mishandle the request, leading to a crash or unresponsiveness, effectively denying service to legitimate users. The root cause likely involves improper validation or parsing of the Content-Length header against the actual payload size, which can cause buffer mismanagement or resource exhaustion. No CVSS score has been assigned yet, and no patches or known exploits are currently available. The vulnerability does not require authentication, meaning any attacker capable of sending HTTP requests to the server can attempt exploitation. This makes the attack vector relatively straightforward, especially if the server is exposed to the internet or untrusted networks. Outsystems Platform Server is used to develop and manage enterprise applications, so disruption can impact business-critical services. The lack of authentication and user interaction requirements increases the risk profile, as automated attacks could be feasible. The vulnerability was reserved in late September 2025 and published in December 2025, indicating recent discovery and disclosure.

For European organizations, this vulnerability poses a significant risk to service availability, especially for those relying on Outsystems Platform Server for critical business applications. A successful DoS attack could lead to downtime, loss of productivity, and potential financial losses. Organizations in sectors such as finance, healthcare, government, and manufacturing that use Outsystems for internal or customer-facing applications may experience operational disruptions. The inability to process legitimate requests could also damage reputation and customer trust. Since the attack requires no authentication, attackers could exploit this vulnerability remotely if the server is accessible from untrusted networks. This increases the risk of widespread disruption, particularly in organizations with internet-facing Outsystems deployments. Additionally, the downtime could indirectly affect compliance with European regulations such as GDPR if service interruptions impact data availability or processing. The absence of known exploits currently provides a window for proactive mitigation, but the ease of exploitation suggests attackers may develop exploits soon.

1. Monitor network traffic for anomalous HTTP requests with mismatched Content-Length headers and block suspicious sources using web application firewalls (WAFs) or intrusion prevention systems (IPS). 2. Restrict access to Outsystems Platform Server to trusted networks and implement network segmentation to reduce exposure to untrusted sources. 3. Apply strict input validation and rate limiting on HTTP requests to prevent malformed or excessive requests from reaching the server. 4. Engage with Outsystems support or vendor channels to obtain patches or updates addressing this vulnerability as soon as they become available. 5. Implement robust incident response plans to quickly detect and mitigate DoS attacks, including failover and redundancy mechanisms to maintain service availability. 6. Conduct regular vulnerability assessments and penetration testing focused on HTTP protocol handling to identify similar weaknesses. 7. Educate IT and security teams about this specific vulnerability to ensure rapid response and mitigation readiness.