CVE-2024-39949 is a high-severity vulnerability affecting Dahua NVR4XXX series network video recorders (NVRs) with build times before December 13, 2023. The vulnerability is classified as CWE-617 (Reachable Assertion) and CWE-20 (Improper Input Validation). It arises because the affected Dahua NVR devices do not properly validate certain crafted data packets sent to their vulnerable interfaces. An attacker can exploit this flaw by sending specially crafted network packets to the device, triggering an assertion failure within the software. This assertion failure causes the device to crash, resulting in a denial of service (DoS) condition. The CVSS 3.1 base score is 7.5, reflecting a high severity level due to the network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction needed (UI:N). The impact is limited to availability (A:H), with no confidentiality or integrity impact reported. No known exploits are currently in the wild, and no patches have been linked yet. The vulnerability affects all NVR4XXX devices built before the specified date, which are commonly used for video surveillance and security monitoring in various sectors. The root cause is improper input validation leading to a reachable assertion failure, which is a programming error where an assertion statement can be triggered by external input, causing the program to abort unexpectedly. This vulnerability could be leveraged by attackers to disrupt video surveillance operations by causing device crashes, potentially impacting security monitoring and incident response capabilities.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on Dahua NVR4XXX devices for critical security infrastructure such as physical security in corporate offices, government buildings, transportation hubs, and public spaces. A successful exploitation would cause the NVR devices to crash, leading to loss of video recording and monitoring capabilities. This downtime could create blind spots in surveillance coverage, increasing the risk of undetected security incidents or physical breaches. Organizations in sectors such as finance, healthcare, critical infrastructure, and public administration could face operational disruptions and compliance challenges due to interrupted surveillance. Additionally, the denial of service could be used as part of a larger attack campaign to distract or disable security monitoring while other malicious activities are conducted. Although the vulnerability does not directly compromise confidentiality or integrity, the loss of availability of surveillance data can have serious security implications. Given that no authentication or user interaction is required, attackers can remotely exploit this vulnerability over the network, increasing the risk of widespread impact if devices are exposed to untrusted networks or the internet.

To mitigate this vulnerability, European organizations should first identify all Dahua NVR4XXX devices in their environment and verify their build dates. Since no official patches are currently linked, organizations should contact Dahua support or their vendors to obtain firmware updates or security advisories addressing CVE-2024-39949. In the interim, network-level mitigations should be applied: restrict network access to the NVR devices by implementing strict firewall rules that limit incoming traffic to trusted management networks only. Disable any unnecessary network services or interfaces on the affected devices to reduce the attack surface. Employ network segmentation to isolate NVR devices from general user networks and the internet. Monitor network traffic for unusual or malformed packets targeting the NVR interfaces, which could indicate exploitation attempts. Additionally, organizations should implement robust incident response plans to quickly detect and recover from potential device crashes. Regular backups of configuration and recorded video data should be maintained to minimize operational impact. Finally, consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection capabilities tuned to detect attempts to exploit this vulnerability once such signatures become available.