CVE-2026-6198: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-6198 Overview

CVE-2026-6198 is a stack-based buffer overflow vulnerability in the Tenda F456 router running firmware version 1.0.0.5. The flaw resides in the fromNatStaticSetting function handling requests to the /goform/NatStaticSetting endpoint. Attackers manipulate the page argument to overflow a fixed-size stack buffer. The vulnerability is remotely exploitable over the network and requires only low-level authentication. Public disclosure of the exploit details increases the likelihood of opportunistic attacks against exposed devices. The weakness maps to [CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer].

Critical Impact
Remote attackers can corrupt stack memory on the router, potentially achieving arbitrary code execution and full device compromise.

Affected Products

Tenda F456 router, firmware version 1.0.0.5
Web management interface endpoint /goform/NatStaticSetting
Devices exposing the management interface to untrusted networks

Discovery Timeline

2026-04-13 - CVE-2026-6198 published to NVD
2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6198

Vulnerability Analysis

The vulnerability exists in the fromNatStaticSetting handler within the Tenda F456 web management daemon. When a user submits a request to /goform/NatStaticSetting, the handler reads the page parameter from the HTTP request and copies it into a fixed-size stack buffer without validating the input length. Supplying an oversized page value overruns the stack frame, overwriting saved registers and the return address. On embedded MIPS or ARM targets such as the F456, this class of overflow typically allows attackers to redirect execution and execute attacker-controlled instructions. The vendor has not published an advisory in the referenced data.

Root Cause

The root cause is the absence of bounds checking on attacker-controlled input copied into a stack-allocated buffer. The handler uses unsafe string-copy semantics on the page argument, classified under [CWE-119]. No length validation, canary, or input sanitization protects the destination buffer.

Attack Vector

An attacker with network access to the router's management interface and valid low-privilege credentials sends a crafted POST request to /goform/NatStaticSetting. The request includes an oversized page parameter designed to overflow the stack buffer. Successful exploitation can crash the httpd service or, with a tailored payload, achieve arbitrary code execution in the context of the web server, which typically runs as root on consumer routers.

No verified proof-of-concept code is available in the referenced data. Technical reproduction details are published in the GitHub vulnerability documentation and the VulDB entry #357120.

Detection Methods for CVE-2026-6198

Indicators of Compromise

HTTP POST requests to /goform/NatStaticSetting containing abnormally long page parameter values
Unexpected restarts or crashes of the router web management daemon (httpd)
New outbound connections from the router to unfamiliar external hosts following management requests
Unauthorized changes to NAT static mapping configuration

Detection Strategies

Inspect HTTP traffic destined for router management interfaces for oversized form parameters, particularly page values exceeding expected lengths
Deploy network intrusion detection signatures that flag long parameter buffers targeting /goform/ endpoints on Tenda devices
Correlate router availability anomalies with preceding management plane HTTP activity

Monitoring Recommendations

Log all administrative HTTP requests to router management endpoints and forward them to a centralized analytics platform
Alert on repeated 5xx responses or service restarts from the router web interface
Monitor for management interface exposure on WAN-facing IP addresses using external attack surface scans

How to Mitigate CVE-2026-6198

Immediate Actions Required

Restrict access to the router's web management interface to trusted internal hosts only, and disable WAN-side administration
Change default administrative credentials and enforce strong unique passwords to reduce abuse of low-privilege access
Place affected Tenda F456 devices behind a perimeter firewall that filters inbound traffic to TCP/80 and TCP/443
Audit existing NAT static mapping entries for unauthorized modifications

Patch Information

No vendor patch is referenced in the available data. Tenda has not published an advisory for CVE-2026-6198 in the referenced sources. Consult the Tenda official website for firmware updates and replace the device if no fix is released.

Workarounds

Disable remote management features on the router until a patched firmware version is available
Segment the router management VLAN from user and guest networks to limit lateral exposure
Replace end-of-life or unpatched Tenda F456 units with currently supported hardware where feasible
Implement an ACL on upstream equipment to drop traffic to /goform/NatStaticSetting from untrusted sources

bash

# Example upstream firewall rule to restrict router admin access
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 \
  -m iprange ! --src-range 10.0.0.10-10.0.0.20 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 \
  -m iprange ! --src-range 10.0.0.10-10.0.0.20 -j DROP