XML Entity Expansion Attack

Anandhu Krishnan
Published on
14 May 2024


A Billion Laughs attack is an exponential entity expansion that can cripple parsers of markup languages like XML or YAML, leading to denial-of-service (DoS) attacks.


To prevent this type of attack, you can limit the memory allocated per parser, allowing for potential document loss. Alternatively, treat entities symbolically and expand them on an as-needed basis.

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Written by
Anandhu Krishnan
Anandhu Krishnan
Lead Engineer
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