CVE-2026-53755

The Docker API server applied its SSRF destination check to the crawl target URL only, not to the proxy address. An unauthenticated request could supply a proxy pointing at an internal IP and route the browser through it, reaching internal services and cloud-metadata endpoints, while using a perfectly valid crawl URL. The Docker API is unauthenticated by default.

Affected paths

/crawl, /crawl/stream, and /crawl/job accept a browser_config (and crawler_config). The following all feed Chromium's egress and were unchecked:

• browser_config.proxy_config.server
• browser_config.proxy (deprecated field)
• crawler_config.proxy_config.server
• --proxy-server / --proxy-pac-url / --proxy-bypass-list / --host-resolver-rules flags in browser_config.extra_args

Attack

An attacker sends /crawl with a benign, validation-passing URL but a proxy_config.server pointing at an internal IP. Chromium routes all requests through that proxy. For plain-HTTP targets the proxy receives the full request and can return any content, which is then returned verbatim in the crawl result (results[0].html / cleaned_html / markdown). In a real deployment the proxy would be an attacker-controlled server pointing at cloud metadata (e.g. AWS IMDSv1 at 169.254.169.254) to retrieve IAM credential tokens.

Workarounds

• Upgrade to the patched version (0.8.9).
• Enable authentication (CRAWL4AI_API_TOKEN).
• Restrict the container's outbound network access (egress firewall / no metadata route).

Credits

Geo (geo-chen) - reported the proxy_config.server SSRF with a clear PoC.

Unauthenticated server-side request forgery to internal services and cloud-metadata endpoints, with the response returned to the attacker.

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2026-53755 has a CVSS score of 8.6 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.8.9); upgrading removes the vulnerable code path.

Kodem intelligence

Every proxy destination is validated with the same global-routability check used for crawl URLs (reject any resolved address that is not is_global, including IPv6 transition forms) before the browser is constructed; proxy/DNS-redirecting flags are stripped from extra_args. A legitimate public proxy still works. Honors CRAWL4AI_ALLOW_INTERNAL_URLS.

1. What is CVE-2026-53755? CVE-2026-53755 is a high-severity server-side request forgery (SSRF) vulnerability in crawl4ai (pip), affecting versions <= 0.8.8. It is fixed in 0.8.9. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. How severe is CVE-2026-53755? CVE-2026-53755 has a CVSS score of 8.6 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of crawl4ai are affected by CVE-2026-53755? crawl4ai (pip) versions <= 0.8.8 is affected.
4. Is there a fix for CVE-2026-53755? Yes. CVE-2026-53755 is fixed in 0.8.9. Upgrade to this version or later.
5. Is CVE-2026-53755 exploitable, and should I be worried? Whether CVE-2026-53755 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-53755 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-53755? Upgrade crawl4ai to 0.8.9 or later.