CVE-2025-52887 is a high-severity vulnerability affecting version 0.21.0 of the cpp-httplib library, a C++11 single-file header-only cross-platform HTTP/HTTPS library developed by yhirose. The vulnerability is classified under CWE-400, which pertains to uncontrolled resource consumption. Specifically, the issue arises when an attacker sends a large number of HTTP header fields in a request. The vulnerable version of cpp-httplib does not impose any limits on the number of headers it processes, nor does it properly release the memory allocated for these headers after the connection is closed. This leads to a gradual exhaustion of system memory resources, potentially causing the server to crash or become unresponsive due to resource depletion. The vulnerability can be exploited remotely without authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The impact is limited to availability (A:H), with no direct impact on confidentiality or integrity. The issue was addressed in version 0.22.0 of the library, which includes a patch that enforces limits on header processing and ensures proper memory release. No known exploits are currently reported in the wild, but the ease of exploitation and the potential for denial-of-service conditions make this a significant risk for systems using the affected version of cpp-httplib in production environments.

For European organizations, the impact of this vulnerability can be substantial, especially for those relying on cpp-httplib 0.21.0 in their web services or embedded HTTP servers. An attacker can trigger a denial-of-service (DoS) by exhausting server memory, leading to service outages and degraded availability. This can disrupt business operations, cause loss of customer trust, and potentially violate service-level agreements (SLAs). Critical infrastructure providers, financial institutions, and public sector services that depend on stable HTTP services could face operational interruptions. Additionally, recovery from such crashes may require manual intervention, increasing operational costs and downtime. Although the vulnerability does not directly compromise data confidentiality or integrity, the availability impact alone can have cascading effects on dependent systems and services. Given the cross-platform nature of cpp-httplib, the threat spans multiple operating systems and deployment environments common in European IT infrastructures.

To mitigate this vulnerability, organizations should immediately upgrade to cpp-httplib version 0.22.0 or later, which contains the official patch. If upgrading is not immediately feasible, implement network-level protections such as rate limiting and filtering to restrict the number of HTTP headers accepted per request. Deploy Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) configured to detect and block anomalous HTTP header patterns indicative of resource exhaustion attempts. Additionally, monitor server memory usage and connection metrics closely to identify unusual spikes that may signal exploitation attempts. For custom implementations using cpp-httplib, developers should implement internal limits on the number of headers processed and ensure proper memory management on connection termination. Regularly audit and update third-party libraries to incorporate security patches promptly. Finally, incorporate this vulnerability into incident response plans to ensure rapid detection and remediation if exploitation is suspected.