CVE-2020-35498 is a high-severity vulnerability identified in multiple versions of Open vSwitch (OVS), specifically versions 2.5.12 through 2.14.2. Open vSwitch is an open-source multilayer virtual switch commonly used to enable network automation through programmatic extensions, and it is widely deployed in data centers, cloud environments, and virtualized infrastructures. The vulnerability stems from a limitation in the userspace packet parsing implementation. A malicious actor can craft specially malformed packets that cause the kernel's megaflow—a data structure used to optimize packet processing—to become excessively wide. This abnormal expansion can exhaust kernel resources, leading to a denial of service (DoS) condition by overwhelming the system's ability to handle network traffic. The vulnerability does not impact confidentiality or integrity but directly threatens system availability. Exploitation requires no privileges (PR:N) and no user interaction (UI:N), and the attack vector is network-based (AV:N), meaning an attacker can exploit this remotely by sending malicious packets to a vulnerable system. The scope is unchanged (S:U), indicating the impact is limited to the vulnerable component without affecting other system components. The CVSS v3.1 base score is 7.5, reflecting a high severity primarily due to the ease of exploitation and the potential for significant service disruption. There are no known public exploits in the wild, and no patches are linked in the provided data, suggesting organizations should verify their OVS versions and apply vendor patches or mitigations where available. Given OVS's role in virtualized network environments, this vulnerability could disrupt critical network functions and services relying on OVS for traffic switching and routing.

For European organizations, the impact of CVE-2020-35498 can be substantial, particularly for those operating large-scale virtualized environments, cloud service providers, telecommunications infrastructure, and enterprises relying on software-defined networking (SDN). A successful exploitation could lead to denial of service on network components, causing outages or degraded performance of critical applications and services. This can affect availability of cloud-hosted services, internal communications, and data center operations. Industries such as finance, healthcare, and government, which depend heavily on network reliability and uptime, could face operational disruptions and potential regulatory compliance issues due to service unavailability. Additionally, organizations using OVS in multi-tenant environments risk cross-tenant impact if a malicious tenant triggers the vulnerability. The lack of confidentiality or integrity impact reduces risks of data breaches but does not diminish the operational risks associated with network downtime. Given the network-based attack vector and no requirement for authentication, the vulnerability could be exploited by external attackers scanning for vulnerable OVS instances exposed to untrusted networks.

1. Immediate verification of Open vSwitch versions in use across all network and virtualized infrastructure components is critical. Identify any deployments running affected versions (2.5.12 through 2.14.2). 2. Apply vendor-provided patches or updates to the latest secure OVS versions as soon as they become available. If official patches are not yet released, consider upgrading to versions beyond 2.14.2 where the vulnerability is fixed. 3. Implement network segmentation and strict ingress filtering to limit exposure of OVS instances to untrusted networks, reducing the attack surface. 4. Monitor network traffic for anomalous or malformed packets that could indicate attempts to exploit the vulnerability, using IDS/IPS systems tuned for OVS-specific traffic patterns. 5. Employ rate limiting and traffic shaping on interfaces connected to OVS to mitigate potential flooding with crafted packets. 6. For cloud and multi-tenant environments, enforce tenant isolation and monitor tenant traffic for suspicious activity. 7. Regularly review and update incident response plans to include scenarios involving OVS-based denial of service attacks. 8. Engage with OVS community and vendors for timely security advisories and best practice configurations to harden OVS deployments.