CVE-2017-8331

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 adding new port forwarding rules to the device. It seems that the POST parameters passed in this request to set up routes on the device can be set in such a way that would result in passing commands to a system API in the function and thus result in command injection on the device. 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_43C280in IDA pro is identified to be receiving the values sent in the POST request and the value set in POST parameter ip_address is extracted at address 0x0043C2F0. The POST parameter ipaddress is concatenated at address 0x0043C958 and this is passed to a system function at address 0x00437284. This allows an attacker to provide the payload of his/her choice and finally take control of the device.

Weakness

The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

Affected Software

Extended Description

Command injection vulnerabilities typically occur when:

Many protocols and products have their own custom command language. While OS or shell command strings are frequently discovered and targeted, developers may not realize that these other command languages might also be vulnerable to attacks. Command injection is a common problem with wrapper programs.

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/136.html
• https://cwe.mitre.org/data/definitions/15.html
• https://cwe.mitre.org/data/definitions/183.html
• https://cwe.mitre.org/data/definitions/248.html
• https://cwe.mitre.org/data/definitions/40.html
• https://cwe.mitre.org/data/definitions/43.html
• https://cwe.mitre.org/data/definitions/75.html
• https://cwe.mitre.org/data/definitions/76.html

References

• http://packetstormsecurity.com/files/153227/Securifi-Almond-2015-Buffer-Overflow-Command-Injection-XSS-CSRF.html
• https://github.com/ethanhunnt/IoT_vulnerabilities/blob/master/Securifi_Almond_plus_sec_issues.pdf
• https://seclists.org/bugtraq/2019/Jun/8