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

Affected: unclecode crawl4ai

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.

GHSA-4qqr-vv2q-cmr5 — Crawl4AI: SSRF filter bypass in Docker server via IPv6 transition forms (NAT64 / 6to4 / unspecified / v4-mapped)

Affected: PyPI: crawl4ai

### 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…

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

GHSA-4qqr-vv2q-cmr5 — Crawl4AI: SSRF filter bypass in Docker server via IPv6 transition forms (NAT64 / 6to4 / unspecified / v4-mapped)