CVE-2017-8329 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 a name for the 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 at address 0x00412CE4 (routerSummary) in the binary "webServer" located in Almond folder, 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 $ra register value on the stack which allows an attacker to control the device by executing a payload of an attacker's choice. If the firmware version AL-R096 is dissected using binwalk tool, we obtain a cpio-root archive which contains the filesystem set up on the device that contains all the binaries. The binary "goahead" is the one that has the vulnerable function that receives the values sent by the POST request. If we open this binary in IDA-pro we will notice that this follows a MIPS little endian format. The function sub_00420F38 in IDA pro is identified to be receiving the values sent in the POST parameter "mssid_1" at address 0x0042BA00 and then sets in the NVRAM at address 0x0042C314. The value is later retrieved in the function at address 0x00412EAC and this results in overflowing the buffer as the function copies the value directly on the stack.
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Analysis
by VulDB Data Team • 10/06/2023
The vulnerability identified in CVE-2017-8329 represents a critical stack buffer overflow affecting Securifi Almond, Almond+, and Almond 2015 devices running firmware version AL-R096. This issue stems from inadequate input validation within the web server component that processes wireless network configuration parameters. The flaw specifically manifests when the device accepts a "mssid_1" POST parameter through the web interface, which is used to set the wireless network name or SSID. The device stores this value in non-volatile RAM and later retrieves it during the processing of network status requests. The vulnerability occurs because the firmware fails to implement proper string length validation on user-supplied input before storing and subsequently copying it to stack buffers during function execution. This oversight creates a predictable buffer overflow condition that can be exploited to overwrite the return address register ($ra) on the stack, effectively allowing remote code execution. The vulnerability is particularly concerning as it affects consumer-grade IoT devices that are often deployed in home networks without proper security updates or monitoring.
The technical implementation of this vulnerability follows a well-documented pattern that aligns with CWE-121 Stack-based Buffer Overflow, where insufficient bounds checking allows attackers to overwrite adjacent memory locations including function return addresses. The exploitation process begins with sending a maliciously crafted POST request containing an excessively long payload in the "mssid_1" parameter, which is then stored in NVRAM at address 0x0042C314. When the device subsequently processes a request to view network status, the vulnerable function at address 0x00412EAC retrieves this stored value and directly copies it to a stack buffer without proper bounds checking. The function routerSummary located at address 0x00412CE4, which is called during this process, serves as the primary vector for the overflow. The MIPS little-endian architecture of the device's firmware further compounds the risk as the stack layout and memory addressing patterns make precise control of execution flow more achievable. The binary goahead contains the vulnerable code path that receives the parameter at sub_00420F38 function, with the value being copied to the stack at address 0x0042BA00 and then later retrieved at address 0x00412EAC, creating the exploitable condition.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass full device compromise and potential network infiltration. An attacker who successfully exploits this vulnerability can gain persistent control over the affected IoT device, potentially using it as a pivot point to access other devices on the same network. This represents a significant concern for home network security, as these devices typically lack robust security controls and may be deployed in unsecured environments. The vulnerability affects devices that are often left unpatched for extended periods, making them attractive targets for persistent attackers. The exploitation requires minimal network access and can be performed remotely without requiring physical presence or specialized equipment. This aligns with ATT&CK framework tactics including TA0001 Initial Access through network-based attacks and TA0002 Execution through code injection techniques. The affected devices may also be used in larger botnet operations, where compromised units can be orchestrated to perform distributed denial-of-service attacks or serve as command-and-control nodes.
Mitigation strategies for CVE-2017-8329 should focus on immediate firmware updates from the vendor, as this vulnerability has been addressed in subsequent firmware releases. Network segmentation and monitoring should be implemented to detect anomalous behavior from affected devices, including unexpected network traffic patterns or attempts to access unauthorized services. The vulnerability highlights the importance of implementing proper input validation and bounds checking in embedded systems, particularly those following the principle of least privilege. Organizations should consider deploying network-based intrusion detection systems that can identify exploitation attempts targeting known IoT vulnerabilities. Device manufacturers should implement comprehensive security testing including fuzzing and static analysis of firmware components before deployment. The vulnerability also underscores the need for regular security audits of IoT device firmware and the importance of maintaining up-to-date security patches for consumer devices. Network administrators should establish monitoring procedures to detect and respond to exploitation attempts, including logging and analyzing web server access patterns for suspicious parameter values that may indicate buffer overflow attempts.