CAPEC-664

Standard Abstraction Level
Meta — Very abstract, high-level category
Standard — Specific enough to understand
Detailed — Tied to specific technique Stable MITRE CAPEC Status
Stable — Fully reviewed and complete
Draft — Under development
Incomplete — Partially defined
Deprecated — No longer recommended
Obsolete — Replaced by another CAPEC Likelihood: High Severity: High
Server Side Request Forgery

Description

An adversary exploits improper input validation by submitting maliciously crafted input to a target application running on a server, with the goal of forcing the server to make a request either to itself, to web services running in the server’s internal network, or to external third parties. If successful, the adversary’s request will be made with the server’s privilege level, bypassing its authentication controls. This ultimately allows the adversary to access sensitive data, execute commands on the server’s network, and make external requests with the stolen identity of the server. Server Side Request Forgery attacks differ from Cross Site Request Forgery attacks in that they target the server itself, whereas CSRF attacks exploit an insecure user authentication mechanism to perform unauthorized actions on the user's behalf.

Prerequisites

Server must be running a web application that processes HTTP requests.

Mitigations

Handling incoming requests securely is the first line of action to mitigate this vulnerability. This can be done through URL validation.

Further down the process flow, examining the response and verifying that it is as expected before sending would be another way to secure the server.

Allowlist the DNS name or IP address of every service the web application is required to access is another effective security measure. This ensures the server cannot make external requests to arbitrary services.

Requiring authentication for local services adds another layer of security between the adversary and internal services running on the server. By enforcing local authentication, an adversary will not gain access to all internal services only with access to the server.

Enforce the usage of relevant URL schemas. By limiting requests be made only through HTTP or HTTPS, for example, attacks made through insecure schemas such as file://, ftp://, etc. can be prevented.

Skills Required

[Medium] The adversary will have to detect the vulnerability through an intermediary service or specify maliciously crafted URLs and analyze the server response.

[High] The adversary will be required to access internal resources, extract information, or leverage the services running on the server to perform unauthorized actions such as traversing the local network or routing a reflected TCP DDoS through them.