FreeRTOS-Plus-TCP is a lightweight TCP/IP stack for FreeRTOS. FreeRTOS-Plus-TCP versions 4.0.0 through 4.1.0 contain a buffer over-read issue in the DNS Response Parser when parsing domain names in a DNS response. A carefully crafted DNS response with domain name length value greater than the actual domain name length, could cause the parser to read beyond the DNS response buffer. This issue affects applications using DNS functionality of the FreeRTOS-Plus-TCP stack. Applications that do not use DNS functionality are not affected, even when the DNS functionality is enabled. This vulnerability has been patched in version 4.1.1.
Weakness
The product reads data past the end, or before the beginning, of the intended buffer.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Freertos-plus-tcp |
Amazon |
4.0.0 (including) |
4.1.1 (excluding) |
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.
- To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.
References