An Unquoted Search Path vulnerability has been identified in the utility for Moxa’s industrial computers (Windows). Due to the unquoted path configuration in the SerialInterfaceService.exe utility, a local attacker with limited privileges could place a malicious executable in a higher-priority directory within the search path. When the Serial Interface service starts, the malicious executable could be run with SYSTEM privileges. Successful exploitation could allow privilege escalation or enable an attacker to maintain persistence on the affected system. While successful exploitation can severely impact the confidentiality, integrity, and availability of the affected device itself, there is no loss of confidentiality, integrity, or availability within any subsequent systems.
Weakness
The product uses a search path that contains an unquoted element, in which the element contains whitespace or other separators. This can cause the product to access resources in a parent path.
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