Netis NC63 Router Unauthenticated Stack Buffer Overflow (netis.cgi ipFilterList)

Technical Analysis

CVE-2026-76071 is a stack-based buffer overflow in netis.cgi's ipFilterList=mod handler, triggered by supplying an oversized destHost parameter that is copied into a fixed-size stack buffer using widthless sscanf conversions without bounds checking. Because the vulnerable code path executes before authentication is enforced, remote attackers can send a single crafted HTTP request to overwrite the stack and hijack control flow. The Boa web server hosting the CGI process runs with root privileges, so successful exploitation grants attackers full root-level code execution on the device, enabling persistent implants, traffic interception, or use of the device as a pivot/proxy. This class of vulnerability is consistent with common IoT/router firmware exploitation patterns (e.g., similar to Mirai-style CGI overflow bugs) and is likely to be weaponized quickly given the low complexity and lack of authentication. Organizations running AI agents or automated pipelines behind or through compromised Netis NC63 routers face risk of traffic interception, credential/API key theft, and man-in-the-middle manipulation of agent-to-cloud or agent-to-tool communications, making this agent-relevant for any edge network hosting agentic infrastructure.

Affected Systems

Netis NC63 wireless routers running firmware through version V3.0.0.3327; specifically the netis.cgi component and Boa web server configuration that executes CGI scripts with root privileges.

Indicators of Compromise

• No confirmed public IOCs at this time; monitor for anomalous HTTP POST/GET requests to netis.cgi with ipFilterList=mod action and oversized destHost parameter values.
• Unexpected outbound connections from Netis NC63 devices
• Unauthorized changes to router IP filter/firewall rules
• Unexpected root shell processes spawned from boa web server process

Remediation Steps

1. 1

   Apply firmware update

   Check Netis vendor advisories for a patched firmware release beyond V3.0.0.3327 and apply immediately once available.

2. 2

   Restrict management interface access

   Disable remote/WAN access to the router's web management interface (netis.cgi) and restrict access to trusted LAN IPs only.

3. 3

   Network segmentation

   Place vulnerable Netis devices behind additional firewalling and segment them away from critical infrastructure, including any hosts running AI agent or automation workloads.

4. 4

   Monitor and detect

   Deploy network intrusion detection signatures for oversized destHost parameters in ipFilterList requests and monitor for anomalous CGI process behavior.

5. 5

   Device replacement consideration

   If vendor patching is unavailable or delayed, consider replacing affected devices with actively supported hardware, especially in environments handling sensitive agent-to-cloud traffic.