CVE-2026-76008: Comfast CF-N1-S Buffer Overflow Flaw

CVE-2026-76008 Overview

CVE-2026-76008 is a stack-based buffer overflow in the Comfast CF-N1-S wireless device running firmware version 2.6.0.1. The flaw resides in the get_para_from_uri function of /cgi-bin/mbox-config, which handles URI parameter parsing. Attackers can manipulate the width and height arguments to overflow a stack buffer. The vulnerability is remotely exploitable over the network without authentication or user interaction. The issue is tracked under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact
Unauthenticated remote attackers can trigger a stack-based buffer overflow via crafted URI parameters, potentially leading to arbitrary code execution on affected Comfast CF-N1-S devices.

Affected Products

Comfast CF-N1-S firmware version 2.6.0.1
Component: URI Parameter Parsing (get_para_from_uri function)
Endpoint: /cgi-bin/mbox-config

Discovery Timeline

2026-08-19 - CVE-2026-76008 published to NVD
2026-08-20 - Last updated in NVD database

Technical Details for CVE-2026-76008

Vulnerability Analysis

The vulnerability affects the CGI handler /cgi-bin/mbox-config on Comfast CF-N1-S devices. The get_para_from_uri function extracts parameter values from the request URI but does not enforce length checks on values assigned to the width and height parameters. When an attacker supplies oversized strings for these arguments, the function writes beyond the bounds of a fixed-size stack buffer.

Stack-based buffer overflows of this kind can overwrite adjacent stack data, saved registers, and the return address. On embedded Linux devices such as consumer wireless equipment, this class of flaw commonly leads to remote code execution as the web server process, which typically runs with elevated or root privileges. The EPSS probability is currently 0.574%.

Root Cause

The root cause is missing input validation in get_para_from_uri. The function copies attacker-controlled URI parameter values into a stack buffer without bounds checking, violating the memory boundary requirements described in CWE-119.

Attack Vector

Exploitation requires only network access to the device's web management interface. An attacker sends a crafted HTTP request to /cgi-bin/mbox-config containing oversized width or height parameters in the URI. No authentication or user interaction is required. Refer to the VulDB entry for CVE-2026-76008 and the associated GitHub repository for additional technical details.

Detection Methods for CVE-2026-76008

Indicators of Compromise

HTTP requests to /cgi-bin/mbox-config containing unusually long width or height URI parameters
Crashes, reboots, or unexpected restarts of the device web server process
Outbound connections from the router to unfamiliar external hosts following inbound requests to the CGI endpoint

Detection Strategies

Inspect web server and reverse proxy logs for requests to /cgi-bin/mbox-config with parameter values exceeding expected lengths
Deploy network intrusion detection signatures that flag oversized query string parameters targeting Comfast CGI endpoints
Correlate device crash telemetry with preceding HTTP requests to identify exploitation attempts

Monitoring Recommendations

Restrict management interface exposure and monitor administrative traffic to consumer wireless devices
Alert on repeated malformed HTTP requests targeting /cgi-bin/ paths on IoT devices
Track firmware versions across the fleet to identify assets running Comfast CF-N1-S 2.6.0.1

How to Mitigate CVE-2026-76008

Immediate Actions Required

Remove Comfast CF-N1-S 2.6.0.1 devices from untrusted networks and block internet exposure of the web management interface
Restrict access to /cgi-bin/mbox-config to trusted management hosts using upstream firewall or ACL rules
Inventory affected devices and monitor vendor channels for a firmware update addressing CVE-2026-76008

Patch Information

At the time of publication, no vendor patch has been referenced in the NVD entry or VulDB advisory. Organizations should track the Comfast vendor site and the referenced advisories for firmware updates.

Workarounds

Place affected devices behind a segmented network and disable remote/WAN-side administration
Enforce upstream web application firewall rules that reject requests to /cgi-bin/mbox-config with width or height parameter values exceeding a strict length threshold
Replace end-of-support or unpatched Comfast CF-N1-S devices with supported hardware where feasible

bash

# Example iptables rule: block WAN-side access to the vulnerable CGI endpoint
iptables -A INPUT -i wan0 -p tcp --dport 80 -m string \
  --string "/cgi-bin/mbox-config" --algo bm -j DROP