Introduction
Modern applications constantly communicate with other systems. They fetch images, call APIs, validate links, and integrate third-party services. Because of this, servers make outbound requests all the time. However, this behaviour introduces a serious risk known as SSRF attacks.
Server-Side Request Forgery (SSRF) attacks occur when an application allows attackers to control where the server sends requests. As a result, attackers can reach internal systems that were never meant to be exposed.
In 2026, SSRF attacks remain one of the most dangerous web vulnerabilities because they bypass firewalls, exploit trust, and expose cloud infrastructure from the inside.
This guide explains how SSRF attacks work, why internal systems get exposed, and how organisations can reduce the risk.
What Is Server-Side Request Forgery (SSRF)?
Server-Side Request Forgery (SSRF) is a vulnerability that allows attackers to make a server send requests to unintended destinations.
Instead of attacking a system directly, the attacker tricks the server into doing it for them.
In simple terms:
- The application accepts a URL or network input
- The server fetches the resource on behalf of the user
- The attacker manipulates the destination
Because the request originates from the server, it often has access to internal networks and trusted services.
Why SSRF Is Especially Dangerous
SSRF attacks are dangerous because they abuse trust and networkposition, not software flaws alone.
Servers sit inside trusted networks
Servers can access internal IPs, services, and metadata endpoints.
Firewalls trust outbound traffic
Many security controls focus on inbound traffic, not server-initiated requests.
Cloud environments amplify the risk
Cloud platforms expose sensitive internal services that SSRF can reach.
As a result, SSRF attacks often lead to severe secondary compromise.
How SSRF Attacks Work
Although implementations vary, SSRF attacks follow a common flow.
Step 1: User-controlled input is accepted
The application allows input such as:
- URLs
- Image links
- Webhooks
- File fetch locations
Step 2: The server makes a request
The backend fetches the resource without validating the destination properly.
Step 3: The attacker manipulates the target
Instead of an external URL, the attacker supplies:
- Internal IP addresses
- Localhost references
- Cloud metadata endpoints
Step 4: Internal systems respond
The server receives sensitive data and returns it to the attacker.
Because the request looks legitimate, security controls rarely intervene.
Common SSRF Attack Targets
SSRF attacks focus on internal systems that were never designed for exposure.
Internal APIs
Administrative APIs often lack authentication because they are assumed to be private.
Cloud metadata services
Cloud platforms expose metadata endpoints containing credentials and configuration details.
Databases and caches
Internal services like Redis or Elasticsearch are common SSRF targets.
Local services
Localhost services running on the same server become reachable.
Each exposed service increases the blast radius of the attack.
Real-World SSRF Scenario
A web application allows users to upload profile pictures via URL. The backend fetches the image and stores it.
An attacker submits a URL pointing to an internal metadata service. The server fetches it successfully and returns the response.
Within seconds, the attacker gains access to cloud credentials that allow further compromise.
No firewall rules were bypassed. No malware was deployed. The server simply followed instructions.
This scenario shows why SSRF attacks are so effective.
Why SSRF Attacks Are Hard to Detect
SSRF attacks blend into normal application behaviour.
Requests originate from trusted servers
Logs show valid internal traffic.
No suspicious payloads exist
There is no obvious exploit code.
Responses look legitimate
Sensitive data appears as normal responses.
Attack paths vary
Different services expose different risks.
Because of this, SSRF vulnerabilities often remain hidden for long periods.
Impact on Businesses and Individuals
For Businesses
- Exposure of internal services
- Cloud credential theft
- Infrastructure compromise
- Data breaches
- Regulatory and compliance risks
- Loss of customer trust
For Individuals
- Exposure of personal data
- Account compromise
- Privacy violations
- Long-term security consequences
Why SSRF Is a Cloud Security Problem
SSRF attacks have become more severe because of cloud architecture.
Metadata endpoints contain secrets
Cloud metadata services often expose access tokens.
Microservices trust internal traffic
Internal communication is rarely authenticated.
Automation magnifies damage
Compromised credentials enable rapid escalation.
Therefore, SSRF attacks often become full cloud breaches.
How to Prevent SSRF Attacks
Reducing SSRF risk requires strict controls.
Validate and restrict outbound requests
Allow only known domains and protocols.
Block internal IP ranges
Prevent access to localhost and private networks.
Disable unnecessary fetch features
Remove unused URL-fetch functionality.
Harden cloud metadata access
Apply strict access controls and isolation.
Monitor outbound traffic
Unexpected destinations indicate abuse.
Design with zero trust assumptions
Never assume internal requests are safe.
Detailed SSRF prevention guidance is provided by OWASP, which highlights SSRF as a critical web vulnerability: Read more
Why SSRF Is a Design Flaw, Not Just a Bug
SSRF vulnerabilities often arise from design assumptions. Developers assume servers should fetch whatever users provide. However, that assumption ignores how much power servers actually have.
Therefore, preventing SSRF requires rethinking trust boundaries, not just adding filters.
Conclusion
SSRF attacks expose internal systems by turning trusted servers into attack tools. By abusing server-side requests, attackers bypass firewalls, reach private services, and compromise cloud environments.
In 2026, SSRF attacks remain a serious threat because modern applications depend heavily on outbound connectivity. By validating requests, restricting internal access, and designing with zero trust principles, organisations can significantly reduce SSRF risk. At eSHIELD IT Services, we help teams identify SSRF exposure early and secure internal systems before attackers do.
FAQ
What is an SSRF attack?
It forces a server to make requests to unintended destinations.
Why are SSRF attacks dangerous?
They expose internal systems that should never be public.
Are SSRF attacks common in cloud apps?
Yes, especially in applications that fetch URLs.
Do firewalls stop SSRF?
Usually not, because the request originates internally.
Can SSRF lead to full cloud compromise?
Yes, especially through metadata services.
Is SSRF a client-side attack?
No, it occurs entirely on the server side.
Are APIs vulnerable to SSRF?
Yes, if they fetch user-controlled URLs.
Is input validation enough to prevent SSRF?
No, network-level restrictions are also required.
