CVE-2026-24112 is a buffer overflow vulnerability identified in the Tenda W20E router firmware version V4.0br_V15.11.0.6. The vulnerability stems from improper input validation in the 'addWewifiWhiteUser' function, which processes the 'userInfo' parameter using the 'sscanf' function without enforcing size constraints. 'sscanf' reads formatted input into fixed-size buffers, and without size checks, an attacker can supply an overly long 'userInfo' string to overwrite adjacent memory. This classic buffer overflow (CWE-120) can lead to memory corruption, causing the device to crash or behave unpredictably, resulting in denial of service (DoS). The vulnerability is remotely exploitable over the network without requiring authentication or user interaction, increasing its risk profile. The CVSS v3.1 base score is 7.5 (high), reflecting the network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability (no confidentiality or integrity impact). No patches or known exploits have been reported yet, but the vulnerability's presence in a widely used consumer router model suggests potential for future exploitation. The lack of authentication requirements means attackers can target vulnerable devices directly if exposed to untrusted networks. The vulnerability highlights the importance of secure coding practices, especially input validation when using unsafe functions like 'sscanf'.

The primary impact of CVE-2026-24112 is denial of service due to device crashes or instability caused by buffer overflow memory corruption. For organizations relying on Tenda W20E routers, this can disrupt network connectivity, degrade service availability, and potentially interrupt business operations. Since the vulnerability does not affect confidentiality or integrity, data theft or manipulation is unlikely. However, the ease of remote exploitation without authentication means attackers can launch DoS attacks from anywhere, potentially targeting critical network infrastructure or consumer environments. In large-scale deployments, such as ISPs or enterprises using these routers for edge connectivity, widespread exploitation could cause significant outages. The absence of known exploits currently reduces immediate risk, but the vulnerability's characteristics make it a likely target for future attack tool development. Additionally, denial of service on network devices can be leveraged as part of larger multi-stage attacks or to distract security teams. The impact is especially severe in environments where these routers are exposed to the internet or untrusted networks without adequate segmentation or firewall protections.

1. Immediate mitigation should focus on restricting access to the router's management interfaces by implementing network segmentation and firewall rules to block unauthorized inbound traffic, especially from untrusted networks or the internet. 2. Disable remote management features if not required to reduce the attack surface. 3. Monitor network traffic for unusual or malformed packets targeting the 'addWewifiWhiteUser' function or related endpoints, which may indicate exploitation attempts. 4. Contact Tenda support or check official channels regularly for firmware updates or patches addressing this vulnerability, and apply them promptly once available. 5. If patching is delayed, consider replacing vulnerable devices with alternative hardware from vendors with timely security support. 6. Employ network intrusion detection/prevention systems (IDS/IPS) with signatures tuned to detect buffer overflow attempts or anomalous input patterns targeting this vulnerability. 7. Educate network administrators about the risks of exposing consumer-grade routers directly to untrusted networks and enforce best practices for device hardening. 8. Conduct regular vulnerability assessments and penetration testing to identify and remediate similar issues proactively.