CVE-2025-2620: D-Link DAP-1620 Buffer Overflow Vulnerability

CVE-2025-2620 Overview

A critical stack-based buffer overflow vulnerability has been identified in D-Link DAP-1620 firmware version 1.03, affecting the mod_graph_auth_uri_handler function within the /storage component of the Authentication Handler. This vulnerability allows remote attackers to trigger a buffer overflow through network-accessible requests, potentially leading to complete device compromise including arbitrary code execution.

The vulnerability is particularly concerning because it affects an end-of-life product that is no longer supported by D-Link, meaning no official security patches will be released. The exploit details have been publicly disclosed, increasing the risk of active exploitation in the wild.

Critical Impact

Unauthenticated remote attackers can exploit this stack-based buffer overflow to achieve complete device compromise, potentially enabling network pivoting, traffic interception, or denial of service on affected D-Link DAP-1620 devices.

Affected Products

• D-Link DAP-1620 Firmware version 1.03
• D-Link DAP-1620 Hardware (all revisions running vulnerable firmware)

Discovery Timeline

• 2025-03-22 - CVE-2025-2620 published to NVD
• 2025-03-26 - Last updated in NVD database

Technical Details for CVE-2025-2620

Vulnerability Analysis

This vulnerability exists in the mod_graph_auth_uri_handler function, which is responsible for processing authentication requests within the device's web interface. The function fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer, resulting in 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).

When an attacker sends a specially crafted request to the /storage endpoint, the overflow can corrupt adjacent stack memory including saved return addresses and stack frame pointers. This enables an attacker to hijack program execution flow and potentially execute arbitrary code with the privileges of the web server process, which typically runs with elevated privileges on embedded devices.

Root Cause

The root cause is improper bounds checking in the mod_graph_auth_uri_handler function. The function allocates a fixed-size buffer on the stack for processing URI parameters but does not verify that incoming data fits within this allocated space. When oversized input is provided, the data overflows beyond the buffer boundaries, corrupting critical stack structures.

This type of vulnerability is common in embedded device firmware where memory-safe programming practices may not be consistently applied, and legacy C code operates without modern compiler protections or runtime bounds checking.

Attack Vector

The attack can be initiated remotely over the network without requiring any authentication. An attacker simply needs network access to the device's management interface, which may be exposed on the local network or, in misconfigured deployments, accessible from the internet.

The exploitation flow typically involves:

1. The attacker crafts a malicious HTTP request targeting the /storage endpoint
2. The oversized payload is passed to mod_graph_auth_uri_handler
3. The function copies the payload into a stack buffer without length validation
4. Stack memory is corrupted, overwriting the return address
5. When the function returns, execution jumps to attacker-controlled code

Since no verified code examples are available, technical details about specific exploitation techniques can be found in the Notion Document Vulnerability Report and VulDB entry #300622.

Detection Methods for CVE-2025-2620

Indicators of Compromise

• Unexpected device reboots or crashes indicating potential exploitation attempts
• Anomalous outbound connections from the DAP-1620 device to unknown IP addresses
• Modified device configuration or firmware that was not authorized by administrators
• Unusual traffic patterns or HTTP requests to the /storage endpoint with oversized payloads

Detection Strategies

• Monitor network traffic for unusually large HTTP requests targeting D-Link DAP-1620 devices on the /storage path
• Implement intrusion detection rules to flag requests with excessively long URI parameters or POST data
• Deploy network-based anomaly detection to identify potential buffer overflow exploitation patterns
• Use asset inventory tools to identify all D-Link DAP-1620 devices in your environment

Monitoring Recommendations

• Enable verbose logging on network firewalls and IDS/IPS systems monitoring traffic to IoT devices
• Set up alerts for any HTTP 500 errors or service crashes on DAP-1620 devices
• Monitor for firmware modifications or configuration changes on affected devices
• Implement network segmentation monitoring to detect lateral movement if a device is compromised

How to Mitigate CVE-2025-2620

Immediate Actions Required

• Isolate all D-Link DAP-1620 devices from internet-facing networks immediately
• Implement network segmentation to restrict access to device management interfaces
• Consider device replacement as this is an end-of-life product with no vendor support
• Block external access to the device's web management interface using firewall rules

Patch Information

This vulnerability affects the D-Link DAP-1620, which has reached end-of-life status and is no longer supported by D-Link. No official security patch will be released by the vendor. Organizations using this device should plan for immediate replacement with a currently supported product.

For more information on D-Link product support status, visit the D-Link Official Website.

Workarounds

• Disable remote management access and restrict web interface access to trusted internal networks only
• Place the device behind a firewall with strict access control lists limiting management access
• Monitor the device for suspicious behavior and be prepared to disconnect it if exploitation is detected
• Replace the DAP-1620 with a currently supported access point that receives security updates

# Example firewall rule to restrict management access (iptables)
# Block external access to the DAP-1620 management interface
iptables -A FORWARD -d <DAP-1620_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <DAP-1620_IP> -p tcp --dport 443 -j DROP

# Allow management only from trusted admin subnet
iptables -I FORWARD -s 192.168.1.0/24 -d <DAP-1620_IP> -p tcp --dport 80 -j ACCEPT