K50839343 : NGINX ModSecurity WAF vulnerability CVE-2021-42717

Security Advisory Description

ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects. Crafted JSON objects with nesting tens-of-thousands deep could result in the web server being unable to service legitimate requests. Even a moderately large (e.g., 300KB) HTTP request can occupy one of the limited NGINX worker processes for minutes and consume almost all of the available CPU on the machine. Modsecurity 2 is similarly vulnerable: the affected versions include 2.8.0 through 2.9.4. (CVE-2021-42717)

Impact

An attacker using specifically formatted JSON messages can cause high resource utilization and potentially denial-of-service (DoS).