What server-side request forgery is
Server-side request forgery, often abbreviated SSRF, is a web security vulnerability in which an attacker induces a server to make requests to destinations the attacker chooses. Many applications make requests to other resources on a user's behalf. If an attacker can influence where those requests go, they can make the server reach places it was not intended to, which is the essence of SSRF.
How the attack works
SSRF typically occurs when an application takes a destination from user input and then makes a request to it without proper restrictions. An attacker supplies a destination of their choosing, and the server dutifully makes the request there. Because the request originates from the server, it may reach places the attacker could not access directly, turning the server into an unwitting intermediary.
Reaching internal systems
A particularly dangerous aspect of SSRF is that the server may be able to reach internal systems that are not exposed to the outside world. By directing the server's requests inward, an attacker might access resources that would normally be protected behind the network boundary. This ability to pivot through the server to internal targets is a major reason SSRF is taken seriously.
Why it is dangerous
SSRF is dangerous because it abuses the server's position and trust to make requests the attacker could not make on their own. Depending on what the server can reach, the consequences range from accessing sensitive internal resources to other unintended effects. Since the requests come from a trusted server, they may bypass protections that assume requests come from outside, amplifying the risk.
Preventing SSRF
Defending against server-side request forgery involves carefully controlling and validating the destinations a server is allowed to request based on user input. By restricting where the server may make requests and not blindly trusting user-supplied destinations, applications can prevent attackers from redirecting the server's requests to unintended or internal targets. Careful validation is central to the defense.
Why it matters
Server-side request forgery is an important web security vulnerability to understand. Knowing what SSRF is - making a server send requests to attacker-chosen destinations - clarifies a serious class of attacks that abuse a server's reach. For anyone interested in web security, it is a valuable concept to understand.
Related on Skillo
See also: What is cross-site request forgery (CSRF)? Explained, What is a reverse proxy? Explained.
Sources
Published date reflects the original event date (2026-06-09). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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