CVE-2026-4254 in AC8
Summary
by MITRE • 03/16/2026
A weakness has been identified in Tenda AC8 up to 16.03.50.11. This vulnerability affects the function doSystemCmd of the file /goform/SysToolChangePwd of the component HTTP Endpoint. This manipulation of the argument local_2c causes stack-based buffer overflow. The attack can be initiated remotely. The exploit has been made available to the public and could be used for attacks.
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Analysis
by VulDB Data Team • 03/21/2026
The vulnerability CVE-2026-4254 represents a critical stack-based buffer overflow flaw in the Tenda AC8 router firmware version 16.03.50.11 and earlier. This weakness resides within the HTTP endpoint component, specifically in the doSystemCmd function located in the /goform/SysToolChangePwd file path. The vulnerability stems from improper input validation and handling of the local_2c argument, which creates an exploitable condition that allows attackers to manipulate memory layout during function execution. The affected device operates under a web-based management interface that processes user-supplied parameters through the vulnerable HTTP endpoint, making it accessible to remote attackers without requiring physical access or authentication.
The technical exploitation of this vulnerability occurs through a stack-based buffer overflow condition that arises when the local_2c argument exceeds the allocated buffer space within the doSystemCmd function. This type of vulnerability falls under CWE-121 stack-based buffer overflow, which is classified as a serious memory corruption flaw that can lead to arbitrary code execution. The attack vector is remotely accessible, meaning that an attacker can trigger the vulnerability through network-based communication without needing to be physically present at the device. The public availability of exploit code significantly increases the risk profile of this vulnerability, as it removes the technical barriers that typically prevent widespread exploitation. The overflow can potentially overwrite adjacent stack memory locations including return addresses, function pointers, and other critical execution context data that controls program flow.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass complete system compromise and potential network infiltration. An attacker who successfully exploits this vulnerability can gain unauthorized access to the router's underlying operating system, potentially enabling them to modify network configurations, establish persistent backdoors, or use the device as a pivot point for attacking other systems within the local network. The implications are particularly severe given that routers serve as critical network infrastructure devices that control traffic flow and network boundaries. This vulnerability could enable attackers to perform man-in-the-middle attacks, DNS hijacking, or even facilitate broader network reconnaissance and lateral movement activities. The fact that this vulnerability affects a widely deployed consumer router model increases the potential attack surface significantly, as many organizations rely on consumer-grade devices for basic networking functions without proper security hardening.
Mitigation strategies for CVE-2026-4254 should prioritize immediate firmware updates from Tenda, as this represents the most effective defense against the known exploitation vectors. Network administrators should implement network segmentation to isolate affected devices and monitor for suspicious network traffic patterns that might indicate exploitation attempts. The implementation of web application firewalls and input validation controls at network perimeters can provide additional layers of protection, though these measures are less effective against direct exploitation of the device itself. Security monitoring should focus on detecting unusual parameter patterns in HTTP requests targeting the /goform/SysToolChangePwd endpoint, which could indicate exploitation attempts. Organizations should also consider disabling unnecessary web management interfaces and implementing strong network access controls to limit exposure. From an ATT&CK framework perspective, this vulnerability maps to techniques involving command execution and privilege escalation, while the remote access capability aligns with initial access and persistence tactics that threat actors commonly employ in network infiltration campaigns.