CVE-2025-11324: Tenda AC18 Buffer Overflow Vulnerability

CVE-2025-11324 Overview

CVE-2025-11324 is a stack-based buffer overflow vulnerability in the Tenda AC18 wireless router running firmware version 15.03.05.19(6318). The flaw resides in the /goform/setNotUpgrade handler, which fails to validate the length of the newVersion parameter before copying it into a fixed-size stack buffer. Attackers can trigger the overflow remotely over the network, corrupting the call stack and potentially achieving arbitrary code execution on the device. The vulnerability is tracked under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). Public proof-of-concept details are available through a third-party IoT vulnerability research repository.

Critical Impact

Remote attackers can corrupt router memory through the newVersion parameter, leading to denial of service or arbitrary code execution on affected Tenda AC18 routers.

Affected Products

• Tenda AC18 hardware router
• Tenda AC18 firmware version 15.03.05.19(6318)
• Deployments exposing the web management interface to untrusted networks

Discovery Timeline

• 2025-10-06 - CVE-2025-11324 published to NVD
• 2025-10-07 - Last updated in NVD database

Technical Details for CVE-2025-11324

Vulnerability Analysis

The vulnerability exists in the HTTP handler bound to /goform/setNotUpgrade in the Tenda AC18 web management service. The handler reads the newVersion argument from the request and copies it into a stack-allocated buffer without enforcing a length check. Supplying an oversized value overruns the buffer and overwrites adjacent stack data, including saved return addresses. Because the AC18 firmware runs without modern exploit mitigations such as stack canaries or full address-space layout randomization on critical binaries, a crafted payload can redirect execution flow into attacker-controlled memory. Successful exploitation grants control over the router process, which typically runs with elevated privileges on embedded Linux firmware.

Root Cause

The root cause is missing input validation on the newVersion parameter inside the setNotUpgrade form handler. The code path uses an unbounded string copy operation against a fixed-size stack buffer, which is the classic precondition for stack smashing classified under CWE-119.

Attack Vector

An authenticated attacker on the same network as the router can send a crafted HTTP POST request to /goform/setNotUpgrade containing an oversized newVersion value. The request travels through the standard management interface, requires no user interaction, and can be delivered from any host that can reach the router's web service. Refer to the GitHub PoC Repository and VulDB entry #327207 for technical exploitation details.

// No verified exploit code is reproduced here.
// See the linked PoC repository for the full request structure
// that triggers the overflow in /goform/setNotUpgrade.

Detection Methods for CVE-2025-11324

Indicators of Compromise

• HTTP POST requests to /goform/setNotUpgrade containing abnormally long newVersion parameter values
• Unexpected reboots, watchdog resets, or httpd process crashes on Tenda AC18 routers
• Outbound connections from the router to unfamiliar hosts following management-interface traffic spikes
• New or modified firmware configuration entries that did not originate from administrator activity

Detection Strategies

• Inspect web server and router logs for requests targeting /goform/setNotUpgrade and flag those with newVersion values exceeding expected version string lengths
• Deploy network intrusion detection signatures that match oversized newVersion payloads in HTTP traffic to router management interfaces
• Correlate router crash events with preceding inbound HTTP requests from internal or external sources

Monitoring Recommendations

• Capture management-plane traffic to the router and retain it for at least 30 days to support incident review
• Alert on any access attempts to router administrative endpoints from non-administrative VLANs or external IP ranges
• Track firmware integrity and configuration baselines, alerting on deviations from a known-good state

How to Mitigate CVE-2025-11324

Immediate Actions Required

• Restrict access to the Tenda AC18 web management interface to a dedicated administrative network segment
• Disable remote (WAN-side) administration if it is currently enabled on the device
• Rotate router administrator credentials and audit account activity for unauthorized changes
• Monitor the Tenda Official Site for an updated firmware release addressing this issue

Patch Information

No vendor advisory or fixed firmware version has been published at the time of NVD entry. Administrators should track the VulDB CTI ID #327207 record and the Tenda Official Site for firmware updates that supersede 15.03.05.19(6318). Until a patch is released, treat the device as exposed and apply compensating network controls.

Workarounds

• Place the router behind a firewall rule set that blocks inbound HTTP and HTTPS traffic to the management interface from untrusted sources
• Segment IoT and consumer routers onto isolated VLANs to limit lateral movement if the device is compromised
• Replace end-of-support hardware with a model that receives active security updates if no patch becomes available

# Example: restrict access to the router management UI using iptables on an upstream gateway
# Replace 10.0.0.1 with the router IP and 10.0.0.10 with the admin workstation IP
iptables -A FORWARD -p tcp -d 10.0.0.1 --dport 80 -s 10.0.0.10 -j ACCEPT
iptables -A FORWARD -p tcp -d 10.0.0.1 --dport 80 -j DROP
iptables -A FORWARD -p tcp -d 10.0.0.1 --dport 443 -s 10.0.0.10 -j ACCEPT
iptables -A FORWARD -p tcp -d 10.0.0.1 --dport 443 -j DROP