Common Attack Pattern Enumeration and Classification
A Community Resource for Identifying and Understanding Attacks
This attack exploits certain XML parsers which manage data in an inefficient manner. The attacker crafts an XML document with many attributes in the same XML node. In a vulnerable parser, this results in a denial of service condition where CPU resources are exhausted because of the parsing algorithm.
In this example, assume that the victim is running a vulnerable parser such as .NET framework 1.0. This results in a quadratic runtime of O(n^2).
A document with n attributes results in (n^2)/2 operations to be performed. If an operation takes 100 nanoseconds then a document with 100,000 operations would take 500s to process. In this fashion a small message of less than 1MB causes a denial of service condition on the CPU resources.
This attack may be mitigated completely by using a parser that is not using a vulnerable container. Mitigation may also limit the number of attributes per XML element.
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