CVE-2025-48945 is a high-severity use-after-free vulnerability (CWE-416) affecting the Python module pycares, which provides asynchronous DNS resolution capabilities by interfacing with the c-ares C library. Specifically, versions of pycares prior to 4.9.0 are vulnerable due to improper handling of Channel objects during garbage collection. When a Channel object is destroyed while DNS queries are still pending, the underlying memory is freed prematurely, leading to a use-after-free condition. This results in a fatal Python interpreter crash, causing denial of service (DoS) for applications relying on pycares for DNS resolution. The vulnerability does not require authentication or user interaction and can be triggered remotely by sending DNS queries that remain unresolved during Channel object cleanup. The issue has been addressed in pycares version 4.9.0 by implementing a safe channel destruction mechanism that ensures no pending queries exist before freeing memory. The CVSS 4.0 score is 8.2 (high), reflecting the network attack vector, low attack complexity, no privileges or user interaction required, and a high impact on availability due to interpreter crashes. No known exploits are currently reported in the wild, but the vulnerability poses a significant risk to any Python applications using vulnerable pycares versions for asynchronous DNS resolution.

For European organizations, the primary impact is service disruption due to application crashes caused by the use-after-free vulnerability in pycares. Organizations relying on Python-based services or microservices that perform asynchronous DNS queries using pycares versions prior to 4.9.0 may experience denial of service, potentially affecting critical infrastructure, web services, or internal applications. This can lead to downtime, degraded user experience, and operational interruptions. While the vulnerability does not directly lead to data breaches or code execution, the loss of availability can have cascading effects, especially in environments where DNS resolution is critical for service orchestration or security controls. Additionally, attackers could exploit this vulnerability to conduct targeted DoS attacks against specific services, amplifying the impact on business continuity. Given the widespread use of Python in cloud-native applications and automation tools, the vulnerability could affect a broad range of sectors including finance, telecommunications, healthcare, and government services across Europe.

1. Immediate upgrade of pycares to version 4.9.0 or later in all affected environments to ensure the safe channel destruction mechanism is in place. 2. Conduct an inventory of all Python applications and services to identify usage of pycares and verify the version in use. 3. Implement runtime monitoring and alerting for unexpected Python interpreter crashes or service restarts that may indicate exploitation attempts. 4. Employ container or process isolation techniques to limit the blast radius of potential crashes caused by this vulnerability. 5. For environments where immediate upgrade is not feasible, consider temporarily disabling or replacing asynchronous DNS resolution with synchronous alternatives or other libraries not affected by this vulnerability. 6. Review and harden DNS query handling and network controls to limit exposure to untrusted inputs that could trigger the vulnerability. 7. Integrate vulnerability scanning tools into CI/CD pipelines to detect usage of vulnerable pycares versions proactively.