CVE-2025-4354: D-Link DAP-1520 Buffer Overflow Vulnerability

CVE-2025-4354 Overview

A critical stack-based buffer overflow vulnerability has been identified in Tenda DAP-1520 wireless range extender firmware version 1.10B04_BETA02. The vulnerability exists in the check_dws_cookie function within the /storage endpoint, where improper bounds checking during cookie processing allows an attacker to overflow the stack buffer. This flaw enables remote attackers with low-level privileges to potentially achieve full device compromise through network-based attacks.

Critical Impact

Remote attackers can exploit this stack-based buffer overflow to potentially execute arbitrary code, crash the device, or gain unauthorized control over the affected Tenda DAP-1520 range extender, compromising network security.

Affected Products

• Tenda DAP-1520 Firmware version 1.10B04_BETA02
• Tenda DAP-1520 Hardware devices running vulnerable firmware
• D-Link DAP-1520 devices (referenced in CPE data)

Discovery Timeline

• May 6, 2025 - CVE-2025-4354 published to NVD
• May 13, 2025 - Last updated in NVD database

Technical Details for CVE-2025-4354

Vulnerability Analysis

This vulnerability represents a classic stack-based buffer overflow condition (CWE-787: Out-of-bounds Write, CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer) in an embedded IoT device. The check_dws_cookie function processes user-supplied cookie data without adequate validation of input length, allowing attackers to write beyond the allocated stack buffer boundaries.

Stack-based buffer overflows in embedded devices like the DAP-1520 are particularly dangerous because these devices typically lack modern memory protection mechanisms such as ASLR (Address Space Layout Randomization) or stack canaries. The firmware's embedded nature means that successful exploitation can lead to complete device takeover, enabling attackers to intercept network traffic, pivot to other network devices, or establish persistent access.

The attack requires only low-level privileges and can be executed remotely over the network without user interaction, making it highly exploitable in real-world scenarios where these range extenders are deployed in home and small business networks.

Root Cause

The root cause of CVE-2025-4354 lies in the check_dws_cookie function's failure to properly validate the length of cookie data before copying it into a fixed-size stack buffer. When processing HTTP requests to the /storage endpoint, the function allocates a stack buffer of a predetermined size but does not verify that incoming cookie values fit within this allocated space. This allows an attacker to supply an oversized cookie value that overwrites adjacent stack memory, including the function's return address.

Attack Vector

The attack is executed remotely over the network by sending specially crafted HTTP requests to the /storage endpoint on vulnerable Tenda DAP-1520 devices. The attacker constructs a malicious cookie header containing an oversized payload designed to overflow the stack buffer in the check_dws_cookie function.

The attack flow involves:

1. Identifying a vulnerable DAP-1520 device on the network (typically via port scanning or network discovery)
2. Crafting an HTTP request with a malicious cookie value exceeding expected buffer bounds
3. Sending the request to the /storage endpoint
4. The overflow corrupts stack memory, potentially overwriting the return address
5. Upon function return, execution flow can be redirected to attacker-controlled code

For technical details on the vulnerability mechanism, refer to the GitHub PoC Repository and VulDB Entry #307472.

Detection Methods for CVE-2025-4354

Indicators of Compromise

• Unusual HTTP requests to the /storage endpoint containing abnormally large cookie values
• Unexpected device reboots or crashes indicating potential exploitation attempts
• Network traffic anomalies originating from or directed at DAP-1520 devices
• Firmware modification or unexpected configuration changes on the device

Detection Strategies

• Deploy network intrusion detection systems (IDS) with rules to identify oversized HTTP cookie headers targeting /storage endpoints
• Monitor for HTTP requests with cookie lengths exceeding typical thresholds (e.g., >4KB) directed at known DAP-1520 device IPs
• Implement web application firewall rules to inspect and limit cookie header sizes for IoT device management interfaces
• Use SentinelOne Singularity to detect anomalous network behavior patterns associated with IoT exploitation attempts

Monitoring Recommendations

• Establish baseline network traffic patterns for DAP-1520 devices and alert on deviations
• Log all HTTP traffic to IoT device management interfaces for forensic analysis
• Configure SNMP or syslog monitoring on network segments containing vulnerable devices
• Implement network segmentation to isolate IoT devices and enable focused monitoring

How to Mitigate CVE-2025-4354

Immediate Actions Required

• Isolate affected Tenda DAP-1520 devices from untrusted network segments immediately
• Restrict access to the device management interface using firewall rules or access control lists
• Disable remote management features if not required for operations
• Monitor device logs and network traffic for signs of exploitation attempts

Patch Information

As of the last update on May 13, 2025, no official vendor patch has been confirmed for this vulnerability. Administrators should monitor the Tenda Official Website for firmware updates addressing CVE-2025-4354. Given the critical nature of this vulnerability and the public availability of exploit information, organizations should prioritize applying patches as soon as they become available.

Workarounds

• Place DAP-1520 devices behind a firewall that blocks external access to the /storage endpoint
• Implement network segmentation to isolate IoT devices from critical infrastructure
• Use a VPN for remote management instead of exposing the device directly to the internet
• Consider replacing end-of-life or unsupported devices with actively maintained alternatives

# Example firewall rule to block external access to vulnerable endpoint
# Adjust interface and IP addresses for your environment
iptables -A FORWARD -i eth0 -d 192.168.1.100 -p tcp --dport 80 -m string --string "/storage" --algo bm -j DROP
iptables -A FORWARD -i eth0 -d 192.168.1.100 -p tcp --dport 443 -m string --string "/storage" --algo bm -j DROP