title: Apache APISIX: the body_schema check in request-validation plugin can be bypassed
description: In Apache APISIX before 2.13.0, when decoding JSON with duplicate keys, lua-cjson will choose the last occurred value as the result. By passing a JSON with a duplicate key, the attacker can bypass the body_schema validation in the request-validation plugin. For example, `{"string_payload":"bad","string_payload":"good"}` can be used to hide the "bad" input. Systems satisfy three conditions below are affected by this attack: 1. use body_schema validation in the request-validation plugin 2. upstream application uses a special JSON library that chooses the first occurred value, like jsoniter or gojay 3. upstream application does not validate the input anymore. The fix in APISIX is to re-encode the validated JSON input back into the request body at the side of APISIX. Improper Input Validation vulnerability in __COMPONENT__ of Apache APISIX allows an attacker to __IMPACT__. This issue affects Apache APISIX Apache APISIX version 2.12.1 and prior versions.
problem types: CWE-20 Improper Input Validation
affected:
{
product: Apache APISIX
vendor: Apache Software Foundation
versions:
lessThanOrEqual: 2.12.1, status: affected, version: Apache APISIX, versionType: custom
}
metrics:
other: [
content: {'other': 'low'}
type: unknown
]
workarounds: 1. upgrade APISIX to 2.13.0 if you need to use the body_schema validation in the request-validation plugin
2. add additional validation in the application code, embrace defensive programming