Description

Buffer Overflow vulnerability in Shenzhen Jixiang Tengda Technology Co., Ltd. Tenda A18 v.15.13.07.09 allows a remote attacker to execute arbitrary code via the fromSetCmdlineRun function

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-01T17:17:31.270Z",
  "pubdate": "2026-09-01T17:17:31.270Z",
  "executiveSummary": "A buffer overflow vulnerability exists in the Tenda A18 wireless range extender, specifically within the firmware version 15.13.07.09.\nThe vulnerability resides in the 'fromSetCmdlineRun' function, which fails to adequately validate input length before processing, leading to a stack-based memory corruption.\nThis flaw enables a remote, unauthenticated attacker to execute arbitrary code with elevated system privileges.\nSuccessful exploitation compromises the integrity, availability, and confidentiality of the affected device, potentially allowing the attacker to gain full control over the router or facilitate further lateral movement within the local network.\nGiven the nature of the vulnerability, the attack surface is exposed over the network, and exploitation does not require prior authentication, presenting a critical security risk to users of the Tenda A18 device.",
  "technicalDetails": "The vulnerability originates in the 'fromSetCmdlineRun' function within the Tenda A18 firmware (v.15.13.07.09).\nThe root cause is a lack of boundary checking during the handling of user-supplied data transmitted via the web-based administrative interface or associated command-line control parameters.\nWhen the 'fromSetCmdlineRun' function receives an overly long input string, it copies the data into a fixed-size stack buffer without verifying if the input length exceeds the allocated memory space.\nThis behavior triggers a classic stack-based buffer overflow, allowing the attacker to overwrite critical memory structures, including the function's return address on the stack.\nBy crafting a malicious payload, an attacker can control the program counter (EIP/RIP) upon the function's completion.\nThe attack flow typically involves sending a specifically crafted HTTP request or command string to the vulnerable interface, where the payload contains a combination of a NOP sled, a custom shellcode (often designed to open a reverse shell or execute system-level commands), and an overwritten return address pointing to the payload entry point.\nAs the function completes its execution, the overwritten return address diverts the CPU's instruction pointer to the attacker-supplied shellcode stored within the buffer or another memory location accessible by the process.\nBecause the 'fromSetCmdlineRun' function operates with the privileges of the underlying web server or system service, the injected code executes with root-level or administrative-level permissions on the device's embedded operating system.\nThe exploitation does not require authentication, as the vulnerable function is reachable by remote entities through the network-exposed management interface.\nThe post-exploitation impact includes the total compromise of the Tenda A18 device, enabling the attacker to modify device configurations, intercept network traffic, use the device as a pivot point for internal network reconnaissance, or deploy persistent malware within the firmware environment."
}