Vulnerability Database

351,760

Total vulnerabilities in the database

CVE-2026-53754 — Crawl4AI

Server-Side Request Forgery (SSRF)

Summary

The Docker API server's SSRF protection (validate_webhook_url / validate_url_destination in deploy/docker/utils.py) used an explicit IPv4/IPv6 CIDR blocklist that missed several address families. An attacker could reach internal services and cloud metadata endpoints (e.g. 169.254.169.254) despite the filter by encoding an internal IPv4 address inside an IPv6 transition form, or by using the IPv6 unspecified address.

Because the Docker API is unauthenticated by default (jwt_enabled: false), no credentials are required.

Affected paths

The blocklist was applied to crawl URLs (POST /crawl, /md, /html, /screenshot, /pdf, /execute_js) and webhook URLs (/crawl/job, /llm/job). All shared the same incomplete check.

Bypasses

The following all resolve to (or route to) blocked internal addresses but were NOT caught:

  • IPv6 unspecified ::
  • NAT64 64:ff9b::a9fe:a9fe (embeds 169.254.169.254)
  • 6to4 2002:a9fe:a9fe:: (embeds 169.254.169.254)
  • IPv4-mapped ::ffff:169.254.169.254
  • IPv4-compatible ::a9fe:a9fe

The error message also echoed the resolved internal IP, acting as a minor DNS/oracle leak.

Impact

Server-Side Request Forgery: an unauthenticated attacker can make the server fetch internal-network URLs and cloud instance-metadata endpoints, potentially exposing internal services and cloud credentials.

Fix

The blocklist is replaced by a single rule: reject any resolved IP where not ip.is_global, evaluated on the address AND every embedded IPv4 transition form (v4-mapped, NAT64 64:ff9b::/96, 6to4 2002::/16, v4-compat ::/96). Error messages are now opaque and no longer echo the resolved IP.

Workarounds

  • Upgrade to the patched version.
  • Enable authentication (CRAWL4AI_API_TOKEN).
  • Restrict the container's outbound network access (egress firewall / no metadata route).

Credits

Internal security audit (Crawl4AI maintainers).

CVSS v3:

  • Severity: High
  • Score: 7.5
  • AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CWEs:

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.