A command injection vulnerability exists in the D-Link DIR-882 Router firmware DIR882A1_FW102B02 within the prog.cgi and rc binaries. The sub_432F60 function in prog.cgi stores user-supplied SetSysLogSettings/IPAddress values in NVRAM via nvram_safe_set(SysLogRemote_IPAddress, ...). These values are later retrieved in the sub_448DCC function of rc using nvram_safe_get and concatenated into a shell command executed via twsystem() without any sanitization. An unauthenticated remote attacker can exploit this vulnerability to execute arbitrary commands on the device through specially crafted HTTP requests to the routers web interface.
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.
Extended Description
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.
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.
References