RIPd in Quagga 0.98 and 0.99 before 20060503 does not properly implement configurations that (1) disable RIPv1 or (2) require plaintext or MD5 authentication, which allows remote attackers to obtain sensitive information (routing state) via REQUEST packets such as SEND UPDATE.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.