7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-53754

CVE-2026-53754: Crawl4AI: SSRF filter bypass in Docker server via IPv6 transition forms (NAT64 / 6to4 / unspecified / v4-mapped)

Crawl4AI is an open-source LLM friendly web crawler & scraper. Prior to 0.8.8, 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. This vulnerability is fixed in 0.8.8.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-53754

CVE-2026-53754:

7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation NoneAutomatable YesTech Impact Partial

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
crawl4ai	pip	<= 0.8.7	0.8.8

Technical Details

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Miggo AI

Root Cause Analysis

The vulnerability is a Server-Side Request Forgery (SSRF) in the crawl4ai package, specifically within the Docker API server. The root cause is an incomplete validation mechanism for URLs provided by the user. The functions validate_webhook_url and its wrapper validate_url_destination in deploy/docker/utils.py were intended to prevent requests to internal network resources. However, the implementation had two main flaws:

Incomplete Blocklist: The validation relied on an explicit blocklist of CIDR ranges which was not exhaustive.
Insufficient IPv6 Handling: The helper function _expand_ip_candidates failed to correctly identify internal IPv4 addresses embedded within various IPv6 transition formats, such as NAT64, 6to4, and the IPv6 unspecified address (::).

An attacker could exploit this by providing a specially crafted URL containing an IPv6 address that, when resolved by the server, would point to an internal service (e.g., 169.254.169.254). Because the validation logic did not recognize these IPv6 formats, the request would be allowed, leading to an SSRF vulnerability.

The patch addresses this by completely replacing the blocklist approach. The new implementation in validate_webhook_url checks if the resolved IP address is a globally routable address using the is_global property. Furthermore, the _expand_ip_candidates function was rewritten to correctly parse and check all relevant IPv6 transition formats. This ensures that any URL resolving to a non-global (i.e., private, reserved, or internal) IP address is blocked, effectively closing the SSRF vulnerability.

Vulnerable functions

validate_webhook_url

deploy/docker/utils.py

This function was responsible for validating webhook and crawl URLs. The vulnerability was due to an incomplete blocklist of private/reserved IP ranges and insufficient handling of IPv6 transition mechanisms, allowing an attacker to bypass the SSRF protection. The function failed to check for several IPv6 address formats that could represent internal IPv4 addresses.

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WAF Protection Rules

WAF Rule

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Reasoning

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