CVE-2025-67835 is a Denial-of-Service vulnerability affecting Paessler PRTG Network Monitor versions prior to 25.4.114. The flaw resides in the Notification Contacts functionality, which can be exploited by an authenticated attacker to trigger resource exhaustion, leading to service disruption. Specifically, this vulnerability falls under CWE-400, indicating that the system can be overwhelmed by excessive resource consumption. The attack vector is network-based (AV:N), requires low attack complexity (AC:L), and privileges (PR:L) but no user interaction (UI:N). The scope is unchanged (S:U), and the impact affects only availability (A:H), with no confidentiality (C:N) or integrity (I:N) impact. While no public exploits are currently known, the vulnerability poses a risk to organizations relying on PRTG for network monitoring and alerting, as a successful DoS could impair their ability to detect and respond to network issues. The lack of an available patch at the time of reporting necessitates interim mitigation strategies. The vulnerability was reserved in December 2025 and published in January 2026, indicating recent discovery and disclosure.

For European organizations, this vulnerability could disrupt critical network monitoring operations, potentially delaying detection of network outages or security incidents. Organizations in sectors such as telecommunications, finance, energy, and government, which rely heavily on continuous network monitoring, may experience operational impacts if the DoS is exploited. Although the vulnerability requires authentication, insider threats or compromised credentials could be leveraged to launch attacks. The unavailability of monitoring services could lead to cascading failures or delayed incident response, increasing the risk of broader security incidents or operational downtime. The medium severity rating reflects the limited scope to availability but highlights the importance of network monitoring in maintaining organizational resilience.

1. Restrict access to the Notification Contacts functionality to only trusted and necessary users, employing the principle of least privilege. 2. Monitor logs and system behavior for unusual activity related to Notification Contacts usage that could indicate attempts to exploit the vulnerability. 3. Implement strong authentication mechanisms, including multi-factor authentication, to reduce the risk of credential compromise. 4. Isolate the PRTG Network Monitor server within a segmented network zone to limit exposure. 5. Regularly back up configuration and monitoring data to enable rapid recovery in case of service disruption. 6. Stay informed on Paessler’s official channels for patches or updates addressing this vulnerability and apply them promptly once available. 7. Consider temporary disabling or limiting the Notification Contacts feature if feasible until a patch is released.