Strawberry GraphQL's Bypass of MaxAliasesLimiter via Fragment Spreads leading to GraphQL Alias Amplification

QFinch assessment

The MaxAliasesLimiter extension in Strawberry fails to account for the multiplicative/amplification effect of FragmentSpreadNode. While it correctly counts static aliases within the AST it does not consider how many times a fragments internal aliases are expanded during execution. this allows an attacker to bypass alias limits and force the server to resolve and render a significantly higher number of aliases than allowed, potentially leading to a dos via resource exhaustion.

Potential impact

An attacker can bypass security constraints to cause Application-level DOS. By staying just under the maxaliascount limit in the AST an attacker can trigger thousands of actual alias resolutions on the backend consuming excessive CPU and memory

Technical context

The current implementation of alias counting in strawberry/extensions/maxaliases.py uses a static approach When a FragmentSpread is used multiple times, the actual number of aliases processed by the execution engine is Total Aliases = query aliases + (num of spreads aliases within fragment) Because Strawberry only performs a static sum of the text, it misses this multiplication