The commit diff shows the vulnerability was patched by explicitly setting allErrors: false in Ajv's configuration within lib/validation.js. The buildSchemaCompiler function previously enabled allErrors: true in Fastify's default Ajv options, which made validation processes collect all errors instead of failing fast. This could be exploited by malicious schemas to cause CPU/memory exhaustion. The function's direct control over Ajv's error reporting behavior matches the vulnerability description and patch evidence.