CVE-2026-76868: Netcore NR255-V Null Pointer DoS Vulnerability

CVE-2026-76868 Overview

CVE-2026-76868 is a null pointer dereference vulnerability [CWE-476] in the Netcore NR255-V router running firmware version 1.5.130703. The flaw resides in the route_policy_add.cgi endpoint, which fails to validate the presence of the exit_port parameter before dereferencing it. Authenticated attackers can send a crafted HTTP request that omits the exit_port field, causing the CGI process to crash and producing a denial-of-service condition on the router.

Critical Impact
A single malformed request to route_policy_add.cgi crashes the routing policy service on the Netcore NR255-V, disrupting network availability until the device recovers or is restarted.

Affected Products

Netcore NR255-V router
Firmware version 1.5.130703
route_policy_add.cgi component

Discovery Timeline

2026-09-15 - CVE-2026-76868 published to the National Vulnerability Database (NVD)
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-76868

Vulnerability Analysis

The vulnerability affects the routing policy management interface exposed by the NR255-V web administration service. The route_policy_add.cgi handler parses several parameters from the incoming HTTP request to construct a new policy rule. Among these, the exit_port field identifies the outbound interface for the policy.

When the handler processes a request that lacks the exit_port parameter, the lookup routine returns a null pointer. The CGI then passes this pointer to downstream string-handling logic without checking its validity. Dereferencing the null pointer terminates the CGI worker, disrupting the routing policy service and any concurrent administrative sessions.

Because the vulnerable interface requires administrative authentication, exploitation is limited to users who already hold credentials on the device. However, the attack complexity is low and requires no user interaction.

Root Cause

The root cause is missing input validation on a required parameter. The CGI does not verify that exit_port is present and non-null before it is used, which violates defensive parsing practices for CGI request handlers written in C.

Attack Vector

An authenticated attacker sends an HTTP request to route_policy_add.cgi on the router's management interface with all typical policy fields except exit_port. The absent parameter triggers the null dereference, crashing the CGI process. Repeated requests can be used to sustain the denial-of-service condition. Full technical analysis is available in the GitHub Null Dereference Analysis and the VulnCheck Security Advisory.

// No verified proof-of-concept code is published.
// Refer to the linked advisories for request-level details.

Detection Methods for CVE-2026-76868

Indicators of Compromise

HTTP POST requests to route_policy_add.cgi that omit the exit_port form field.
Repeated CGI process crashes or restarts logged by the router's web administration service.
Unexpected interruptions to the routing policy management interface following administrative activity.

Detection Strategies

Inspect web server access logs on the router for requests to route_policy_add.cgi and correlate them with immediate service faults.
Monitor administrative session activity for repeated failed policy-add operations originating from a single source.
Alert on abnormal restart counts for CGI worker processes on the NR255-V management plane.

Monitoring Recommendations

Forward router syslog and web administration logs to a centralized logging platform for retention and correlation.
Track availability of the router management interface using synthetic health checks that detect service interruption.
Review authenticated administrator activity for unexpected use of policy configuration endpoints.

How to Mitigate CVE-2026-76868

Immediate Actions Required

Restrict access to the router's web administration interface to trusted management networks only.
Rotate administrative credentials and enforce strong, unique passwords for router accounts.
Monitor the vendor's support channels for a firmware update addressing route_policy_add.cgi parameter validation.

Patch Information

No vendor patch is referenced in the published advisory data at the time of writing. Administrators should track the VulnCheck Security Advisory and Netcore vendor communications for firmware releases superseding version 1.5.130703.

Workarounds

Disable remote management on the WAN interface and permit administrative access only from a management VLAN.
Place the router's administrative interface behind a reverse proxy or firewall that enforces required form fields such as exit_port.
Limit the number of accounts with administrative privileges to reduce exposure to authenticated denial-of-service abuse.

bash

# Example: restrict management interface access with an ACL
# Replace 192.0.2.0/24 with your trusted management network
iptables -A INPUT -p tcp --dport 80 -s 192.0.2.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP