Denial of Service via crafted nested query strings

Summary

Faraday is an HTTP client library abstraction layer that provides a common interface over many adapters. From 1.0.0 until 1.10.6 and 2.14.3, Faraday::NestedParamsEncoder, the default nested query parameter encoder/decoder in Faraday, decodes nested query strings without enforcing a maximum nesting depth. A crafted query string causes Faraday to build a deeply nested Ruby Hash structure. The internal dehash routine then recursively walks this attacker-controlled structure without a depth limit. At sufficient depth, Ruby raises an uncaught SystemStackError (stack level too deep), crashing the calling thread or worker. This can lead to denial of service in applications that pass attacker-controlled query strings to Faraday's nested query parsing or URL-building paths. This vulnerability is fixed in 1.10.6 and 2.14.3. A flaw was found in Faraday, an HTTP client library. The Faraday::NestedParamsEncoder, which handles nested query parameters, does not limit the depth of nested query strings during decoding. A remote attacker can exploit this by sending a specially crafted query string, causing the application to build an excessively deep data structure. This can lead to a SystemStackError, resulting in a Denial of Service (DoS) by crashing the application's processing thread or worker. This flaw has an Important impact as applications utilizing the Faraday HTTP client library in Red Hat products are susceptible to a denial of service. A remote attacker can send a specially crafted nested query string, causing the Faraday::NestedParamsEncoder to create an overly deep data structure. This unbounded recursion exhausts system resources, leading to a SystemStackError and crashing the application's processing thread. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-770. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships.