CVE-2025-30256 is a high-severity denial of service (DoS) vulnerability affecting the Tenda AC6 V5.0 router, specifically version V02.03.01.110. The vulnerability arises from improper resource management in the HTTP header parsing functionality, classified under CWE-772 (Missing Release of Resource after Effective Lifetime). An attacker can exploit this flaw by sending a specially crafted sequence of HTTP requests to the device, causing it to exhaust resources and subsequently reboot. This reboot disrupts normal network operations and can lead to temporary loss of connectivity for all devices relying on the affected router. The vulnerability is remotely exploitable over the network without requiring any authentication or user interaction, increasing its risk profile. The CVSS v3.1 score of 8.6 reflects the high impact on availability (A:H) with no impact on confidentiality or integrity, and low attack complexity (AC:L). The scope is changed (S:C), indicating that the vulnerability affects components beyond the initially vulnerable component, potentially impacting the entire device. No known exploits are currently reported in the wild, and no patches have been published yet, which means affected users remain vulnerable. The root cause is the failure to release resources after their effective lifetime during HTTP header parsing, leading to resource exhaustion and forced device reboot.

For European organizations, this vulnerability poses a significant risk to network availability, especially for small and medium enterprises or home office environments that rely on Tenda AC6 V5.0 routers. A successful attack can cause repeated router reboots, resulting in intermittent or prolonged internet outages, disrupting business operations, VoIP communications, and access to cloud services. Critical infrastructure or organizations with remote workforces using these routers may experience productivity losses and potential secondary impacts due to network instability. Although the vulnerability does not directly compromise confidentiality or integrity, the denial of service can be leveraged as part of a broader attack strategy, such as timed disruptions during critical operations or combined with other attacks to increase impact. The lack of authentication and user interaction requirements means attackers can launch attacks remotely and anonymously, increasing the threat surface. Given the router’s typical deployment in consumer and small business environments, the impact on large enterprises may be limited unless these devices are used in branch offices or remote sites.

Immediate mitigation should focus on network-level protections and device configuration adjustments. Organizations should implement network segmentation to isolate vulnerable routers from critical infrastructure and restrict inbound HTTP traffic to management interfaces from untrusted networks. Deploying intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection for unusual HTTP request patterns can help detect and block exploitation attempts. Network administrators should monitor router logs for signs of repeated reboots or abnormal HTTP traffic. Since no official patch is available yet, consider temporarily replacing or upgrading affected devices to newer models or firmware versions once released. Vendors and users should prioritize firmware updates as soon as patches become available. Additionally, disabling remote management over HTTP or restricting it to trusted IP addresses reduces exposure. For environments where replacement is not immediately feasible, implementing rate limiting on HTTP requests to the router can mitigate resource exhaustion attempts. Regular backups of router configurations and network documentation will aid in rapid recovery if devices are compromised or need replacement.