Exploiting SSRF Vulnerabilities: From Detection to RCE
Dec 28, 2023•15 min read
SSRFRCECloud Security
What is SSRF?
Server-Side Request Forgery (SSRF) is a vulnerability that allows an attacker to make requests from the vulnerable server to arbitrary destinations. This can lead to accessing internal services, reading local files, and in some cases, achieving Remote Code Execution (RCE).
Detection Techniques
SSRF vulnerabilities often exist in features that fetch external resources:
- URL preview generators
- Image/file upload from URL
- Webhook integrations
- PDF generators
- API proxies
Exploiting Cloud Metadata Services
One of the most common SSRF exploitation targets is cloud metadata services:
-- AWS metadata endpoint
http://169.254.169.254/latest/meta-data/
-- Retrieve IAM credentials
http://169.254.169.254/latest/meta-data/iam/security-credentials/
-- Azure metadata endpoint
http://169.254.169.254/metadata/instance?api-version=2021-02-01Escalating to RCE
SSRF can be escalated to RCE through various methods:
- Exploiting internal services (Redis, Memcached, etc.)
- Accessing admin panels on localhost
- Chaining with other vulnerabilities
- Exploiting deserialization endpoints
Mitigation Strategies
To protect against SSRF attacks, implement the following controls:
- Whitelist allowed domains and protocols
- Disable unnecessary URL schemas (file://, gopher://, etc.)
- Implement network segmentation
- Use DNS rebinding protection
- Validate and sanitize all user-supplied URLs