CVE-2025-9089 Overview
CVE-2025-9089 is a stack-based buffer overflow vulnerability in the Tenda AC20 router running firmware version 16.03.08.12. The flaw resides in the sub_48E628 function within the /goform/SetIpMacBind endpoint. Attackers can trigger the overflow by manipulating the list argument sent to the affected web interface. The vulnerability is exploitable over the network and a public proof-of-concept has been disclosed, increasing the likelihood of opportunistic exploitation against exposed devices. The weakness is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).
Critical Impact
Remote attackers with low-privileged access can corrupt stack memory on the Tenda AC20 router, potentially leading to arbitrary code execution or denial of service on the affected device.
Affected Products
- Tenda AC20 router (hardware)
- Tenda AC20 firmware version 16.03.08.12
- Endpoint: /goform/SetIpMacBind handler (sub_48E628)
Discovery Timeline
- 2025-08-17 - CVE-2025-9089 published to NVD
- 2025-08-21 - Last updated in NVD database
Technical Details for CVE-2025-9089
Vulnerability Analysis
The vulnerability exists in the HTTP request handler for the IP-MAC binding configuration feature on the Tenda AC20 router. When the device processes a request to /goform/SetIpMacBind, the function sub_48E628 reads the user-supplied list parameter and copies it into a fixed-size stack buffer without proper length validation. The unchecked copy operation overwrites adjacent stack data, including the saved return address and stack frame metadata. An attacker who can reach the router's web management interface can deliver an oversized list value to corrupt execution flow.
Because the AC20 runs a MIPS-based embedded Linux stack with limited exploit mitigations, return-oriented programming or direct shellcode placement is feasible once stack control is achieved. A public proof-of-concept Python exploit script has been published describing the request structure.
Root Cause
The root cause is the absence of bounds checking on the list parameter before it is copied into a stack-allocated buffer inside sub_48E628. The function trusts attacker-controlled input length, violating safe string handling practices and triggering memory corruption when input exceeds the destination buffer size.
Attack Vector
The attack is performed over the network against the router's HTTP management interface. The attacker must hold low-level authenticated access (PR:L) to submit the malicious POST request to the /goform/SetIpMacBind endpoint. Successful exploitation impacts confidentiality, integrity, and availability of the device.
For technical reproduction details, see the published GitHub PoC Python Exploit and the VulDB #320357 Details entry.
Detection Methods for CVE-2025-9089
Indicators of Compromise
- HTTP POST requests to /goform/SetIpMacBind containing abnormally long list parameter values.
- Unexpected reboots, web service crashes, or unresponsive management interfaces on Tenda AC20 devices.
- Outbound connections from the router to unknown external hosts following malformed HTTP requests.
Detection Strategies
- Inspect web server and router syslog entries for repeated 5xx responses or process crashes tied to the goform handler.
- Deploy network IDS signatures that flag POST requests to /goform/SetIpMacBind exceeding expected parameter lengths.
- Monitor management plane traffic for requests originating from non-administrative network segments.
Monitoring Recommendations
- Collect router logs into a centralized log analytics or SIEM platform for correlation across devices.
- Baseline normal administrative request patterns to surface deviations in goform endpoint usage.
- Alert on any external (WAN-side) HTTP requests reaching the router's web interface.
How to Mitigate CVE-2025-9089
Immediate Actions Required
- Disable remote (WAN-side) administration on the Tenda AC20 to limit reachability of the vulnerable endpoint.
- Restrict LAN access to the web management interface to a dedicated administrative VLAN or trusted host list.
- Rotate router administrator credentials, since exploitation requires low-privileged authenticated access.
- Monitor the Tenda Official Website for an official firmware update addressing the issue.
Patch Information
At the time of NVD publication, no vendor patch is referenced in the advisory data. Affected operators should track Tenda firmware release notes for an update superseding version 16.03.08.12 and apply it as soon as it becomes available.
Workarounds
- Place the router management interface behind a firewall rule that blocks untrusted source addresses.
- Replace the affected device with a supported model if a vendor fix is not released in a reasonable timeframe.
- Segment IoT and network infrastructure devices away from user and server networks to limit blast radius.
# Example: restrict access to the Tenda AC20 web UI from upstream firewall
# Allow only the admin workstation (192.0.2.10) to reach the router (10.0.0.1) on TCP/80 and TCP/443
iptables -A FORWARD -s 192.0.2.10 -d 10.0.0.1 -p tcp -m multiport --dports 80,443 -j ACCEPT
iptables -A FORWARD -d 10.0.0.1 -p tcp -m multiport --dports 80,443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
