CVE-2025-4809 Overview
CVE-2025-4809 is a stack-based buffer overflow in the Tenda AC7 wireless router running firmware version 15.03.06.44. The flaw resides in the fromSafeSetMacFilter function handling requests to the /goform/setMacFilterCfg endpoint. Manipulation of the deviceList argument causes memory corruption on the stack. An authenticated remote attacker can trigger the condition over the network, and the exploit has been publicly disclosed. The weakness is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-787 (Out-of-bounds Write).
Critical Impact
Remote attackers with low-privileged access can corrupt router memory through the deviceList parameter, potentially leading to arbitrary code execution or denial of service on the affected device.
Affected Products
- Tenda AC7 router (hardware)
- Tenda AC7 firmware version 15.03.06.44
- Devices exposing the /goform/setMacFilterCfg web management endpoint
Discovery Timeline
- 2025-05-16 - CVE-2025-4809 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-4809
Vulnerability Analysis
The vulnerability exists in the fromSafeSetMacFilter function, which processes MAC address filter configuration requests sent to /goform/setMacFilterCfg on the router's web administration interface. The function reads the user-supplied deviceList parameter and copies it into a fixed-size stack buffer without enforcing adequate length validation. When an attacker submits an oversized deviceList value, the copy operation writes past the buffer boundary and corrupts adjacent stack data, including saved return addresses.
The issue is reachable over the network through standard HTTP requests to the router. Because the affected firmware runs on a MIPS-based embedded Linux system, successful exploitation can result in arbitrary code execution in the context of the web server process, which typically runs with elevated privileges on consumer routers.
Root Cause
The root cause is missing bounds checking before a memory copy operation on attacker-controlled input. The fromSafeSetMacFilter handler does not validate the length of the deviceList parameter against the destination buffer size, satisfying both [CWE-119] and [CWE-787] conditions. This pattern is consistent with other Tenda /goform/ handlers that have historically used unbounded string operations on POST parameters.
Attack Vector
The attack vector is network-based and requires low privileges to reach the affected endpoint. An attacker authenticated to the router's web interface, or one operating from the LAN side where the management portal is accessible, sends a crafted POST request to /goform/setMacFilterCfg containing an oversized deviceList value. The malformed request triggers the overflow during request processing.
No verified exploit code has been published in a structured repository, but a public technical write-up referenced in the Notion Resource Overview and VulDB entry #309264 describes the vulnerable code path and reproduction steps.
Detection Methods for CVE-2025-4809
Indicators of Compromise
- Unexpected HTTP POST requests to /goform/setMacFilterCfg with abnormally long deviceList parameter values
- Router crashes, reboots, or web service unavailability following requests to the MAC filter configuration endpoint
- Unexplained changes in router configuration, DNS settings, or firmware integrity after suspicious management plane traffic
Detection Strategies
- Inspect HTTP traffic to the router's management interface for POST bodies containing deviceList fields exceeding expected MAC address list lengths
- Correlate management endpoint activity with source IPs that are not part of normal administrator workstations
- Monitor router syslog output, where supported, for crashes in the httpd or web management process tied to MAC filter operations
Monitoring Recommendations
- Place affected Tenda AC7 devices behind a network segment where management access is restricted and observable
- Capture and review network flow data targeting TCP/80 and TCP/443 on the router from internal hosts
- Alert on repeated requests to /goform/setMacFilterCfg from a single source within short time windows
How to Mitigate CVE-2025-4809
Immediate Actions Required
- Restrict access to the router's web administration interface to trusted management hosts only, and disable remote WAN-side administration
- Change default and weak administrator credentials to reduce the population of attackers able to reach the authenticated endpoint
- Isolate affected Tenda AC7 devices from sensitive network segments until a vendor fix is applied
Patch Information
As of the last NVD update on 2026-06-17, no fixed firmware version has been listed in the available references. Administrators should monitor the Tenda Official Website and the VulDB entry #309264 for updates and apply firmware patches as soon as they are released.
Workarounds
- Disable the MAC address filtering feature in the router's settings if it is not required, reducing exposure of the vulnerable handler
- Block external access to TCP/80 and TCP/443 on the router at the upstream firewall to prevent unauthenticated network reach
- Consider replacing end-of-support Tenda AC7 hardware with a vendor-supported router that receives regular firmware updates
# Example: restrict router management access to a single admin host using upstream firewall rules
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s <admin_host_ip> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -s <admin_host_ip> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
