Affected: npm: ajv

ajv (Another JSON Schema Validator) through version 8.17.1 is vulnerable to Regular Expression Denial of Service (ReDoS) when the `$data` option is enabled. The pattern keyword accepts runtime data via JSON Pointer syntax (`$data` reference), which is passed directly to the JavaScript `RegExp()` constructor without validation. An attacker can inject a malicious regex pattern (e.g., `\"^(a|a)*$\"`) combined with crafted input to cause catastrophic backtracking. A 31-character payload causes approximately 44 seconds of CPU blocking, with each additional character doubling execution time. This enables complete denial of service with a single HTTP request against any API using ajv with `$data`: true for dynamic schema validation.