Contiki-NG is an open-source, cross-platform operating system for Next-Generation IoT devices. An out-of-bounds read can be caused by an incoming DIO message when using the RPL-Lite implementation in the Contiki-NG operating system. More specifically, the prefix information of the DIO message contains a field that specifies the length of an IPv6 address prefix. The value of this field is not validated, which means that an attacker can set a value that is longer than the maximum prefix length. Subsequently, a memcmp function call that compares different prefixes can be called with a length argument that surpasses the boundary of the array allocated for the prefix, causing an out-of-bounds read. The problem has been patched in the develop branch of Contiki-NG, and is expected to be included in the next release. Users are advised to update as soon as they are able to or to manually apply the changes in Contiki-NG pull request #2721.
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