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CVE-2026-56261 describes a Server-Side Request Forgery (SSRF) vulnerability in Crawl4AI versions prior to 0.8.7. The flaw resides in the Docker API server, specifically within the `/crawl/job` and `/llm/job` endpoints. These endpoints are designed to accept webhook URLs that the server will call upon job completion. However, the application fails to validate or sanitize these user-supplied URLs before making outbound HTTP requests. An unauthenticated attacker can therefore supply a webhook URL pointing to internal or private IP addresses, such as RFC 1918 ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), loopback (127.0.0.1), link-local addresses, or cloud metadata endpoints like 169.254.169.254 (AWS, GCP, Azure instance metadata). When the server processes the job, it will follow the webhook URL and make a request to the attacker‑chosen internal destination. This allows the attacker to probe internal network services, read sensitive information from internal APIs, and, most critically, retrieve cloud instance metadata which often contains temporary credentials, access keys, and configuration secrets. The vulnerability is particularly dangerous because it requires no authentication and can be triggered remotely over the network. The Crawl4AI maintainers addressed the issue in version 0.8.7 by introducing a `validate_webhook_url()` function that implements a blocklist for private, loopback, link-local, and cloud metadata IPs and hostnames. The validation is applied both at job submission time and at the moment the webhook is actually sent. Additionally, the fix explicitly sets `follow_redirects=False` to prevent the server from following redirects that could lead to internal resources. Despite these mitigations, the SSRF filter was found to be bypassable in some cases via IPv6‑mapped IPv4 addresses (e.g., [::ffff:169.254.169.254]), which resolve to the blocked IPv4 addresses, and through the Chromium backend’s own DNS resolution and redirect handling when using the `web_crawl` provider. These bypass techniques highlight the complexity of fully securing SSRF in applications that fetch external resources. The vulnerability is classified as High severity with a CVSS score ranging from 8.6 (CVSS v3) to 9.2 (CVSS v4), reflecting the ease of exploitation and the potential for significant data exposure. Users are strongly advised to upgrade to Crawl4AI 0.8.7 or later, and to consider additional network‑level controls such as firewalls or egress filtering to restrict outbound traffic from the Docker API server.
DailyCVE Form:
Platform: Docker API
Version: < 0.8.7
Vulnerability: SSRF (CWE‑918)
Severity: High (8.6)
date: 2026‑07‑10
Prediction: 0.8.7 released
What Undercode Say:
Check current Crawl4AI version
pip show crawl4ai | grep Version
Test for SSRF via webhook (example using curl)
curl -X POST http://<target>:<port>/crawl/job \
-H "Content-Type: application/json" \
-d '{"url":"https://example.com","webhook":"http://169.254.169.254/latest/meta-data/"}''
Test for IPv6‑mapped IPv4 bypass
curl -X POST http://<target>:<port>/llm/job \
-H "Content-Type: application/json" \
-d '{"url":"https://example.com","webhook":"http://[::ffff:169.254.169.254]/latest/meta-data/"}'
Check if the server resolves internal DNS (e.g., internal.service.local)
curl -X POST http://<target>:<port>/crawl/job \
-H "Content-Type: application/json" \
-d '{"url":"https://example.com","webhook":"http://internal.service.local/"}'
Exploit:
An unauthenticated attacker sends a crafted JSON payload to `/crawl/job` or `/llm/job` with a `webhook` field set to an internal IP, cloud metadata endpoint, or IPv6‑mapped address. The server makes a GET request to that URL, and the response (e.g., cloud credentials) is sent back to the attacker via the webhook callback or can be observed through server logs and error messages. No authentication or special privileges are required.
Protection:
- Upgrade to Crawl4AI version 0.8.7 or later.
- If upgrade is not possible, apply the official patch that adds `validate_webhook_url()` and sets
follow_redirects=False. - Restrict outbound traffic from the Docker API server using network firewalls or egress filters to block access to private IP ranges and metadata endpoints.
- Disable the `web_crawl` provider if not strictly needed, or ensure SSRF guards are applied at the Chromium/Playwright level.
- Monitor server logs for unusual webhook URLs or outbound connection attempts to internal addresses.
Impact:
Successful exploitation allows an attacker to:
- Read cloud instance metadata, potentially exposing temporary AWS/GCP/Azure credentials, access keys, and configuration data.
- Scan internal network services and discover open ports, service banners, and internal API endpoints.
- Access internal services that are not exposed to the public internet, such as databases, caches, or management interfaces.
- Potentially pivot to further internal attacks if the server has access to sensitive internal resources.
- The vulnerability requires no authentication and can be exploited remotely, making it a high‑priority risk for any deployment using the Crawl4AI Docker API.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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