Executive Summary

CVE-2026-6198 is a stack-based buffer overflow vulnerability found in the Tenda F456 router version 1.0.0.5. It occurs in the fromNatStaticSetting function of the HTTP daemon component, which processes a user-supplied parameter called "page."

The vulnerability arises because the "page" parameter is passed directly to the sprintf function without any bounds checking, allowing an attacker to send an excessively long value that overflows the stack buffer.

This overflow can be triggered remotely by sending a specially crafted POST request to the /goform/NatStaticSetting endpoint.

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Impact Analysis

Exploiting this vulnerability can lead to denial of service (DoS) or remote code execution (RCE) on the affected Tenda F456 router.

This means an attacker could crash the device or execute arbitrary code remotely, potentially taking full control of the router.

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Detection Guidance

This vulnerability can be detected by monitoring for suspicious POST requests to the /goform/NatStaticSetting endpoint that contain an unusually long "page" parameter.

A practical detection method is to capture and analyze HTTP traffic targeting the Tenda F456 router, looking specifically for POST requests where the "page" parameter length exceeds normal expected values.

For example, using command-line tools like curl or tcpdump can help detect or reproduce the issue:

• Using curl to test for the vulnerability by sending a large "page" parameter in a POST request: curl -X POST -d "page=$(python3 -c 'print("A"*1000)')" http://<router-ip>/goform/NatStaticSetting
• Using tcpdump to capture HTTP POST requests to the vulnerable endpoint: tcpdump -i <interface> -A 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep '/goform/NatStaticSetting'

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Mitigation Strategies

Immediate mitigation steps include restricting access to the vulnerable endpoint /goform/NatStaticSetting by implementing network-level controls such as firewall rules to block unauthorized or external access.

Additionally, monitoring and filtering HTTP POST requests to ensure that the "page" parameter does not exceed expected lengths can help prevent exploitation.

If possible, update the router firmware to a version that patches this vulnerability or contact the vendor for an official fix.

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Compliance Impact

The provided information does not specify any direct impact of the CVE-2026-6198 vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

However, since the vulnerability allows remote code execution or denial of service on the Tenda F456 router, it could potentially lead to unauthorized access or disruption of network services, which may indirectly affect the security and privacy requirements mandated by such regulations.

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