CVE-2025-1877: D-Link DAP-1562 Firmware RCE Vulnerability

CVE-2025-1877 Overview

CVE-2025-1877 is a null pointer dereference vulnerability in the D-Link DAP-1562 wireless range extender running firmware version 1.10. The flaw resides in the pure_auth_check function within the HTTP POST Request Handler component. An attacker can manipulate the a1 argument to trigger a null pointer dereference, resulting in a denial of service condition on the affected device. The vulnerability is exploitable remotely over the network and the exploit has been publicly disclosed. The D-Link DAP-1562 has reached end-of-life status and is no longer supported by the vendor, meaning no official patch will be released. The flaw is tracked under CWE-476 (NULL Pointer Dereference) and CWE-404 (Improper Resource Shutdown or Release).

Critical Impact

Remote attackers with low-level privileges can crash the HTTP service on affected DAP-1562 devices, disrupting network availability. No vendor patch will be released as the device is end-of-life.

Affected Products

• D-Link DAP-1562 (hardware)
• D-Link DAP-1562 Firmware version 1.10
• End-of-life D-Link wireless range extenders running the affected firmware branch

Discovery Timeline

• 2025-03-03 - CVE-2025-1877 published to the National Vulnerability Database
• 2025-03-06 - Last updated in NVD database

Technical Details for CVE-2025-1877

Vulnerability Analysis

The vulnerability is a null pointer dereference triggered through the pure_auth_check function in the device's HTTP POST request handling logic. When the device processes an HTTP POST request, the handler passes attacker-controlled input as the a1 argument to pure_auth_check. The function fails to validate whether a1 references a valid memory address before dereferencing it. This results in a segmentation fault that crashes the affected service. The attack requires network access to the device's web management interface and low-level authentication, but no user interaction. Successful exploitation yields a high availability impact while leaving confidentiality and integrity unaffected. Because the affected DAP-1562 device is no longer supported, the vulnerability constitutes a permanent risk in any environment still operating the hardware.

Root Cause

The root cause is missing input validation in pure_auth_check. The function dereferences the a1 pointer without confirming the argument points to a valid, initialized object. The associated CWE-476 classification reflects this missing null check, while CWE-404 reflects improper resource cleanup after the crash. Embedded HTTP handlers on consumer networking equipment often lack defensive checks on parsed POST parameters, leaving the parser path exposed when malformed or empty fields are submitted.

Attack Vector

An attacker reaches the vulnerability by sending a crafted HTTP POST request to the DAP-1562 web management interface. The request manipulates the a1 parameter passed to pure_auth_check, causing the function to dereference a null pointer and crash the HTTP service. The attack is conducted remotely over the network and does not require user interaction. Public exploit details have been disclosed in the Notion Analysis on D-Link Vulnerability writeup and tracked in VulDB CTI ID #298191. Repeated exploitation can keep the device's management interface offline and disrupt connectivity for downstream clients.

No verified proof-of-concept code is available for inclusion. Refer to the VulDB entry for technical reproduction details.

Detection Methods for CVE-2025-1877

Indicators of Compromise

• Unexpected restarts or crashes of the HTTP management daemon on DAP-1562 devices
• HTTP POST requests targeting authentication endpoints with malformed or empty parameter values
• Loss of management interface availability immediately following inbound HTTP traffic from untrusted sources
• Network logs showing repeated connection attempts to the device's web administration port from a single source

Detection Strategies

• Monitor network traffic flows toward DAP-1562 administrative interfaces and alert on POST requests from non-administrative subnets
• Inspect HTTP POST bodies destined for pure_auth_check endpoints for missing or anomalous a1 argument values
• Correlate device availability monitoring data with inbound HTTP request patterns to detect crash-and-restart cycles

Monitoring Recommendations

• Enable syslog forwarding from the DAP-1562 to a central log collector and watch for repeated authentication handler errors
• Track ICMP and HTTP availability of the device with uptime monitoring to detect denial of service conditions
• Restrict and audit access to the device management VLAN, alerting on any new sources reaching the web interface

How to Mitigate CVE-2025-1877

Immediate Actions Required

• Identify and inventory all D-Link DAP-1562 devices running firmware 1.10 across the environment
• Remove affected devices from production networks and replace with a currently supported wireless extender model
• Block external and untrusted internal access to the DAP-1562 web management interface at upstream firewalls
• Restrict device administration to a dedicated management VLAN reachable only from authorized administrator hosts

Patch Information

No patch is available. D-Link has confirmed the DAP-1562 is no longer supported, and the vendor will not release fixes for end-of-life products. Asset owners should consult the D-Link Official Website for end-of-life notices and migrate to a supported replacement device.

Workarounds

• Disable remote management on the DAP-1562 and permit administrative access only from a wired, trusted host
• Place the device behind a network firewall that blocks inbound HTTP and HTTPS traffic from untrusted segments
• Apply access control lists (ACLs) on upstream switches to limit which client IPs can reach the device management port
• Plan replacement with a vendor-supported device as the only durable mitigation, since no firmware fix will be issued

# Example firewall rule to restrict access to the DAP-1562 management interface
# Replace <DAP_IP> with the device address and <ADMIN_HOST> with the admin workstation
iptables -A FORWARD -p tcp -d <DAP_IP> --dport 80 -s <ADMIN_HOST> -j ACCEPT
iptables -A FORWARD -p tcp -d <DAP_IP> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <DAP_IP> --dport 443 -s <ADMIN_HOST> -j ACCEPT
iptables -A FORWARD -p tcp -d <DAP_IP> --dport 443 -j DROP