CVE-2025-25664: Tenda AC8 Buffer Overflow Vulnerability

CVE-2025-25664 Overview

CVE-2025-25664 is a critical stack overflow vulnerability discovered in Tenda AC8V4 router firmware version V16.03.34.06. The vulnerability exists within the sub_49E098 function, where improper handling of the shareSpeed parameter allows attackers to overflow the stack buffer. This firmware vulnerability in Tenda's consumer router product line could allow remote attackers to execute arbitrary code or cause denial of service conditions on affected devices.

Critical Impact

Remote attackers can exploit this stack overflow vulnerability to potentially gain complete control over affected Tenda AC8V4 routers, compromising network security and enabling further attacks on connected devices.

Affected Products

• Tenda AC8 Firmware version 16.03.34.06
• Tenda AC8 Hardware version 4.0
• Tenda AC8V4 Router devices running vulnerable firmware

Discovery Timeline

• 2025-02-20 - CVE-2025-25664 published to NVD
• 2025-03-17 - Last updated in NVD database

Technical Details for CVE-2025-25664

Vulnerability Analysis

This vulnerability is classified under CWE-787 (Out-of-bounds Write) and CWE-120 (Buffer Copy without Checking Size of Input). The flaw resides in the sub_49E098 function within the Tenda AC8V4 firmware, which processes the shareSpeed parameter without adequate bounds checking. When a maliciously crafted request containing an oversized shareSpeed value is sent to the router, it triggers a stack buffer overflow condition.

The network-accessible nature of this vulnerability means that attackers do not require authentication or user interaction to exploit it. Successful exploitation could result in complete compromise of the device's confidentiality, integrity, and availability. Given the router's position as a network gateway device, compromise could enable attackers to intercept traffic, pivot to other network devices, or use the router as part of a botnet.

Root Cause

The root cause of CVE-2025-25664 is the absence of proper input validation and bounds checking when copying the shareSpeed parameter into a fixed-size stack buffer within the sub_49E098 function. The firmware fails to verify that the length of user-supplied input does not exceed the allocated buffer size before performing the copy operation, resulting in a classic buffer overflow condition.

Attack Vector

The attack vector is network-based, allowing remote exploitation without authentication. An attacker can craft a malicious HTTP request targeting the vulnerable function endpoint with an oversized shareSpeed parameter. When the vulnerable function processes this parameter, the overflow overwrites adjacent stack memory, potentially including the return address. This enables the attacker to redirect execution flow to attacker-controlled code.

The vulnerability mechanism has been documented in a GitHub PoC Repository that provides additional technical details about the exploitation technique. Attackers typically send a crafted request with a long string value for the shareSpeed parameter that exceeds the expected buffer size, causing the stack overflow condition.

Detection Methods for CVE-2025-25664

Indicators of Compromise

• Unexpected router reboots or instability that may indicate exploitation attempts
• Unusual outbound network connections from the router to unknown external IP addresses
• Abnormally large HTTP requests targeting router management interfaces
• Presence of unfamiliar processes or services running on the router after compromise

Detection Strategies

• Monitor network traffic for anomalous HTTP requests containing oversized parameter values destined for router management interfaces
• Implement intrusion detection rules to identify requests with unusually large shareSpeed parameter values
• Deploy network monitoring to detect any suspicious traffic patterns originating from router devices
• Review router logs for repeated failed requests or crash events that may indicate exploitation attempts

Monitoring Recommendations

• Enable logging on network firewalls to capture traffic to and from router management interfaces
• Configure alerts for router device restarts or service interruptions
• Monitor for firmware modification attempts or unauthorized configuration changes
• Establish baseline network behavior to identify anomalies that may indicate router compromise

How to Mitigate CVE-2025-25664

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not required for operations
• Implement network segmentation to limit potential lateral movement if the router is compromised
• Consider replacing affected devices if no firmware update is available

Patch Information

At the time of publication, no vendor advisory or official patch has been released by Tenda for CVE-2025-25664. Organizations using affected Tenda AC8V4 devices running firmware version V16.03.34.06 should monitor Tenda's official support channels for security updates. Technical details about the vulnerability are available in the GitHub PoC Repository.

Workarounds

• Configure firewall rules to block external access to the router's management interface on ports 80 and 443
• Place the router behind an additional firewall or security appliance that can filter malicious requests
• If feasible, consider deploying alternative router hardware until a patch is available
• Implement network access control to limit which devices can communicate with the router's management interface

# Example firewall rule to restrict management access (adjust for your environment)
# Block external access to router management interface
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP