Envoy Gateway is an open source project for managing Envoy Proxy as a standalone or Kubernetes-based application gateway. In all Envoy Gateway versions prior to 1.2.7 and 1.3.1 a default Envoy Proxy access log configuration is used. This format is vulnerable to log injection attacks. If the attacker uses a specially crafted user-agent which performs json injection, then he could add and overwrite fields to the access log. This vulnerability is fixed in 1.3.1 and 1.2.7. One can overwrite the old text based default format with JSON formatter by modifying the EnvoyProxy.spec.telemetry.accessLog setting.
Weakness
The product does not neutralize or incorrectly neutralizes output that is written to logs.
Extended Description
This can allow an attacker to forge log entries or inject malicious content into logs.
Log forging vulnerabilities occur when:
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
References