ESP-NOW Component provides a connectionless Wi-Fi communication protocol. An Out-of-Bound (OOB) vulnerability was discovered in the implementation of the ESP-NOW group type message because there is no check for the addrs_num field of the group type message. This can result in memory corruption related attacks. Normally there are two fields in the group information that need to be checked, i.e., the addrs_num field and the addrs_list fileld. Since we only checked the addrs_list field, an attacker can send a group type message with an invalid addrs_num field, which will cause the message handled by the firmware to be much larger than the current buffer, thus causing a memory corruption issue that goes beyond the payload length.
Weakness
The product reads data past the end, or before the beginning, of the intended buffer.
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