An improper handling of URL encoding (Hex Encoding) vulnerability has been reported to affect several QNAP operating system versions. If exploited, the vulnerability could allow remote attackers to run the system into unexpected state.
We have already fixed the vulnerability in the following versions:
QTS 5.1.9.2954 build 20241120 and later
QTS 5.2.2.2950 build 20241114 and later
QuTS hero h5.1.9.2954 build 20241120 and later
QuTS hero h5.2.2.2952 build 20241116 and later
Weakness
The product does not properly handle when all or part of an input has been URL encoded.
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