Hunt Ssrf

⚠️ AUTHORIZED USE ONLY This skill is for educational purposes or authorized security assessments only. You must have explicit, written permission from the system owner before using this tool. Misuse of this tool is illegal and strictly prohibited.

Mandatory confirmation gate Before running any command that probes, exploits, changes, persists on, extracts data from, or attempts credential access against a target:

1. Ask the user to state the exact target URL, IP, account, or resource.
2. Ask the user to confirm written authorization and the permitted scope.
3. Show the exact command(s) and explain their expected effect.
4. Wait for explicit confirmation in the current conversation.

Without that confirmation, remain read-only and provide defensive guidance only. Prefer a sandbox, disposable VM, or controlled lab.

Crown Jewel Targets

SSRF is highest-value when the target runs on cloud infrastructure (AWS, GCP, Azure) where metadata services expose credentials, or when the server sits inside a complex internal network (Kubernetes clusters, microservice meshes, internal APIs). Priority targets:

• Cloud-hosted SaaS products (GCP metadata at 169.254.169.254 or metadata.google.internal, AWS IMDSv1)
• Kubernetes/orchestration platforms — aggregated API servers, metrics-server, kubelet endpoints expose privileged cluster operations
• Internal developer tooling — CI/CD, workflow orchestration (Flyte, Argo), admin panels not exposed externally
• Link preview / URL fetching features — Reddit-style preview APIs, Slack-style unfurling, media processors
• Dataset/file import pipelines — anything that fetches remote URLs on behalf of a user
• Enterprise self-hosted software (GitHub Enterprise, GitLab) — SSRF frequently chains to RCE via internal services

Payouts are highest when SSRF reaches: cloud credentials → account takeover, internal admin APIs → data exfil, or chains to RCE.

OOB-Or-It-Didn't-Happen Gate (Read First)

Claims of blind SSRF require an out-of-band (OOB) confirmation. Always. No exceptions.

OOB means: a Burp Collaborator domain, an interactsh-client listener, a canarytoken, or any DNS+HTTP receiver you control that confirms the server actually made an outbound network connection on your behalf.

What is NOT confirmation of SSRF

• The server echoing your URL back in an error message. Example: "The Web application at http://evil.example.com/x could not be found" — this is the server formatting your input into an error string, NOT making an outbound HTTP request. The error came from string formatting, not from network failure.
• The server returning a different status code for an external URL vs localhost. Different error responses can come from URL-scheme validators, not from actual fetching.
• A delayed response when the URL is sent. Delay can come from DNS resolution attempts within the parser, not from completed HTTP fetches.

What IS confirmation of SSRF

• A DNS lookup for your unique Collaborator subdomain appears in the OOB listener.
• An HTTP request to your Collaborator HTTP endpoint with the server's source IP and User-Agent.
• For SSRF in JavaScript-execution contexts (PDF renderers, headless browsers), a fetch from the server to your callback URL.

Default workflow

1. Plant the Collaborator payload first. Sub-tagging (dlsrcurl.<collab>, import.<collab>) only works if your listener actually reports the queried subdomain back to you — verify that before relying on it. Burp's get_collaborator_interactions keys results by payload ID, not by subdomain, so several sub-tags generated from one payload are indistinguishable in the output. When that is the case, generate a fresh payload per candidate parameter and send exactly one request per payload.
2. Send the request to the target endpoint.
3. Wait 30–120 seconds, then poll the OOB listener.
4. Only after a confirmed callback do you claim SSRF.
5. If zero callbacks across all sub-tagged sinks: SSRF claims must be retracted, even if error messages echo URLs.

Lesson from a authorized engagement: SharePoint's /_layouts/15/download.aspx?SourceUrl= returned 500 with the title "The Web application at <attacker-URL> could not be found". Initial scan flagged this as SSRF (server clearly processed the URL). 38 Collaborator-tagged payloads across 12+ URL-accepting parameters yielded zero DNS or HTTP interactions. The "echo" was client-side error-string formatting; the server never made an outbound HTTP request. The path is actually an SP-internal SPFile/SPWebApplication resolver, not a generic URL fetcher. Reporting this as SSRF would have been N/A'd at triage.

Attribute the callback to ONE parameter before reporting

A callback proves the server made a request. It does not tell you which parameter caused it, and the fix depends entirely on that.

BAD   — four candidate fields, one payload, fired in one batch
        -> callbacks arrive, attribution impossible, retest required

GOOD  — fresh payload per field, one request each, poll between
        url      -> callbacks    <- this is the sink
        apiUrl   -> none
        endpoint -> none
        target   -> none

Run the negative control. A parameter that produces no callback is evidence, and it belongs in the report — it is what lets the client fix the right field instead of allowlisting the wrong one.

Lesson from an authorized engagement. A server-side request-forwarding endpoint accepted both url and apiUrl. The application's own stored config used apiUrl, so that was the obvious suspect — but apiUrl was inert and url was the live sink. Batch-firing both had produced callbacks with no attribution; only per-payload isolation identified the real parameter. A report naming apiUrl would have sent the client to patch a field that does nothing.

Blind vs full-read — establish which before scoring

After a callback confirms the request leaves the server, check whether the upstream response body is returned to you. These are different findings:

• Blind (callback only, no body): on the never-submit list standalone. Needs an internal service reached, or data returned, to be reportable.
• Full-read (upstream body in the response): substantially higher severity — read arbitrary internal endpoints directly.

# one request settles it: fetch something with a known, recognisable body
-d '{"url":"https://example.com/"}'
# {"statusCode":200,"data":"<!doctype html>...<title>Example Domain</title>..."}
#                          ^ body returned = full-read, not blind

Also body-diff a known-internal target against a known-external one. A distinct status on a link-local address (e.g. 401 from 169.254.169.254 where every other target returns 200) is the metadata service answering — that proves reach to a non-internet-routable address, which a status code alone otherwise cannot.

Attack Surface Signals

URL Patterns to Hunt

/api/*/preview
/api/*/fetch
/api/*/import
/api/*/webhook
/api/*/proxy
/api/*/render
/api/*/link
/api/*/screenshot
/api/*/export
/api/*/validate
?url=
?uri=
?endpoint=
?redirect=
?src=
?source=
?feed=
?host=
?target=
?dest=
?file=
?path=
?callback=
?image=
?load=
?fetch=

JS Patterns (in client-side code)

// Look for these in JS bundles
fetch(userInput)
axios.get(params.url)
XMLHttpRequest + variable URL
url: req.body.url
src: params.source
href: query.endpoint

Response Header Signals

X-Forwarded-For headers echoed back
Server: internal-service
Via: 1.1 internal-proxy
X-Cache headers revealing internal hostnames

Tech Stack Signals

• Kubernetes — any public-facing aggregated API, metrics endpoints
• GCP — any service fetching URLs that runs on Compute Engine/GKE
• Node.js/Python with URL-fetching libraries (requests, node-fetch, axios)
• Headless browsers (Puppeteer, PhantomJS) used for screenshots/PDF — extremely high value
• XML/DSPL/CSV import features — XXE-style SSRF vector
• OAuth/webhook registration endpoints