A critical buffer overflow vulnerability (CVE-2025-3786) has been identified in Tenda AC15 routers, affecting firmware versions up to 15.03.05.19. The flaw, located in the fromSetWirelessRepeat function of /goform/WifiExtraSet, allows remote attackers to execute arbitrary code by manipulating the mac argument. With a CVSS v3.1 score of 8.8 (High) and public exploit availability, this vulnerability poses significant risks to unpatched devices1.
Technical Breakdown
The vulnerability stems from improper input validation in the wireless repeater configuration function. Attackers can craft a malicious mac parameter to overflow the buffer, potentially leading to remote code execution (RCE). The exploit requires no authentication, making it particularly dangerous for exposed devices. According to VulDB, the issue combines two Common Weakness Enumerations: CWE-119 (memory bounds violation) and CWE-120 (classic buffer overflow)2.
Network scans show approximately 12,000 Tenda AC15 routers accessible via public IPs as of April 2025. The GitHub PoC demonstrates successful exploitation by sending a specially crafted HTTP POST request to /goform/WifiExtraSet with an oversized mac parameter exceeding 128 bytes3.
Mitigation Strategies
Tenda has not released an official patch as of April 18, 2025. Recommended temporary measures include disabling remote management interfaces and segmenting affected routers from critical networks. Organizations should monitor Tenda’s security advisories for firmware updates and consider replacing vulnerable devices if patches are delayed beyond 30 days.
For detection, security teams can look for HTTP requests to /goform/WifiExtraSet with unusually long mac parameters (over 64 characters). SIEM rules should focus on these patterns combined with subsequent suspicious activities like reverse shell attempts.
Impact Assessment
Successful exploitation grants full control over affected routers, enabling attackers to intercept traffic, pivot to internal networks, or deploy persistent malware. The public availability of the exploit increases the likelihood of mass scanning and automated attacks within weeks of disclosure.
This vulnerability is particularly concerning for small businesses and home users who rely on Tenda routers as their primary network gateways. The lack of automatic firmware updates in many consumer-grade devices exacerbates the risk.
Conclusion
CVE-2025-3786 represents a severe threat to Tenda AC15 router deployments. While temporary mitigations exist, the ultimate solution requires vendor-provided firmware updates. Security teams should prioritize identifying affected devices in their asset inventories and implementing network-level protections.
References
- “CVE-2025-3786 Detail.” National Vulnerability Database, 18 Apr. 2025.
- “Technical Analysis of CVE-2025-3786.” VulDB, 18 Apr. 2025.
- “GitHub PoC for Tenda AC15 Exploit.” GitHub, 18 Apr. 2025.
- “Tenda Official Site.” Tenda Technology, accessed 20 Apr. 2025.
