CVE-2017-8335 in Almond
Summary
by MITRE
An issue was discovered on Securifi Almond, Almond+, and Almond 2015 devices with firmware AL-R096. The device provides a user with the capability of setting name for wireless network. These values are stored by the device in NVRAM (Non-volatile RAM). It seems that the POST parameters passed in this request to set up names on the device do not have a string length check on them. This allows an attacker to send a large payload in the "mssid_1" POST parameter. The device also allows a user to view the name of the Wifi Network set by the user. While processing this request, the device calls a function named "getCfgToHTML" at address 0x004268A8 which retrieves the value set earlier by "mssid_1" parameter as SSID2 and this value then results in overflowing the stack set up for this function and allows an attacker to control $ra register value on the stack which allows an attacker to control the device by executing a payload of an attacker's choice. If the firmware version AL-R096 is dissected using binwalk tool, we obtain a cpio-root archive which contains the filesystem set up on the device that contains all the binaries. The binary "goahead" is the one that has the vulnerable function that recieves the values sent by the POST request. If we open this binary in IDA-pro we will notice that this follows a MIPS little endian format. The function sub_00420F38 in IDA pro is identified to be receiving the values sent in the POST parameter "mssid_1" at address 0x0042BA00 and then sets in the NVRAM at address 0x0042C314. The value is later retrieved in the function "getCfgToHTML" at address 0x00426924 and this results in overflowing the buffer due to "strcat" function that is utilized by this function.
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Analysis
by VulDB Data Team • 10/06/2023
The vulnerability described in CVE-2017-8335 represents a critical stack buffer overflow in Securifi Almond and Almond+ devices running firmware version AL-R096. This issue affects wireless network configuration capabilities where devices allow users to set custom network names through a web interface. The vulnerability stems from insufficient input validation in the web server component that processes configuration requests, specifically targeting the mssid_1 POST parameter used for setting wireless network names. The device stores these values in non-volatile RAM and later retrieves them for display purposes, creating an exploitable path from user input to code execution. The flaw manifests when the device processes the getCfgToHTML function which retrieves stored SSID values and uses strcat operations without proper bounds checking, leading to stack corruption.
The technical exploitation of this vulnerability follows a well-defined attack pattern that aligns with CWE-121 Stack-based Buffer Overflow and CWE-787 Out-of-bounds Write categories. The attacker can manipulate the mssid_1 parameter to send oversized payloads that overflow the stack buffer allocated for the getCfgToHTML function at address 0x004268A8. This overflow specifically targets the return address register ($ra) on the stack, allowing arbitrary code execution through a classic return-oriented programming (ROP) or direct code execution attack vector. The vulnerability is particularly concerning because it affects the web server component called "goahead" which handles HTTP requests from network clients. Analysis using binwalk reveals that the firmware contains a cpio-root archive with the complete filesystem, making the vulnerable binary accessible for reverse engineering. The IDA Pro analysis confirms that the vulnerable function sub_00420F38 at address 0x0042BA00 processes the mssid_1 parameter and stores it in NVRAM at address 0x0042C314, later retrieving this data through getCfgToHTML at address 0x00426924 where the strcat operation causes the buffer overflow.
The operational impact of this vulnerability extends beyond simple remote code execution, creating potential for complete device compromise and network infiltration. An attacker with network access can remotely exploit this vulnerability without authentication requirements, potentially gaining persistent access to the device and its network. The attack surface is particularly dangerous because it affects consumer-grade IoT devices that typically lack robust security measures and are often deployed in residential or business environments. This vulnerability can enable attackers to establish persistent backdoors, redirect network traffic, or use the compromised device as a launching point for further attacks against other networked systems. The MIPS little-endian architecture of the vulnerable firmware adds complexity to exploitation but does not prevent successful attack execution. The vulnerability's presence in the goahead web server binary indicates that it affects the core device functionality rather than being a peripheral component, making the impact more severe and harder to isolate. This type of vulnerability directly maps to ATT&CK techniques involving command and control communication, privilege escalation, and persistence mechanisms, as attackers can leverage the device's network capabilities to maintain control over the compromised system.
Mitigation strategies for CVE-2017-8335 should focus on both immediate remediation and long-term security improvements. The most effective immediate solution involves firmware updates from Securifi that implement proper input validation and bounds checking for all user-supplied parameters. Network segmentation and firewall rules can help limit access to affected devices, while monitoring network traffic for unusual patterns may help detect exploitation attempts. Device administrators should disable unnecessary web interfaces and services when possible, and implement network access controls to restrict which systems can communicate with the affected devices. Regular security audits and firmware updates should be implemented as part of ongoing security management. The vulnerability highlights the importance of secure coding practices in embedded systems and demonstrates the critical need for input validation in network-facing components. Organizations should also consider implementing network intrusion detection systems that can identify exploitation attempts targeting known IoT vulnerabilities. Long-term security improvements should include regular firmware updates, secure device configuration practices, and comprehensive vulnerability management programs that address the specific threats faced by IoT deployments.