{"id":"CVE-2026-53754","title":"Crawl4AI: SSRF filter bypass in Docker server via IPv6 transition forms (NAT64 / 6to4 / unspecified / v4-mapped)","summary":"Crawl4AI: SSRF filter bypass in Docker server via IPv6 transition forms (NAT64 / 6to4 / unspecified / v4-mapped)","severity":"high","cvss":7.5,"cwe":["CWE-918"],"vendor":"crawl4ai","product":"crawl4ai","ecosystem":"pip","affected":["crawl4ai <= 0.8.7"],"patched":["crawl4ai 0.8.8"],"published":"2026-06-16","updated":"2026-06-16","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-4qqr-vv2q-cmr5","references":[{"url":"https://github.com/unclecode/crawl4ai/security/advisories/GHSA-4qqr-vv2q-cmr5"},{"url":"https://github.com/advisories/GHSA-4qqr-vv2q-cmr5"}],"tags":["ghsa","pip"],"epss":0.00433,"epssPercentile":0.36999,"ingestedAt":"2026-06-29T14:31:47.696Z","slug":"CVE-2026-53754","body":"## Overview\n\n### Summary\n\nThe 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.\n\nBecause the Docker API is unauthenticated by default (`jwt_enabled: false`), no credentials are required.\n\n### Affected paths\n\nThe 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.\n\n### Bypasses\n\nThe following all resolve to (or route to) blocked internal addresses but were NOT caught:\n- IPv6 unspecified `::`\n- NAT64 `64:ff9b::a9fe:a9fe` (embeds `169.254.169.254`)\n- 6to4 `2002:a9fe:a9fe::` (embeds `169.254.169.254`)\n- IPv4-mapped `::ffff:169.254.169.254`\n- IPv4-compatible `::a9fe:a9fe`\n\nThe error message also echoed the resolved internal IP, acting as a minor DNS/oracle leak.\n\n### Impact\n\nServer-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.\n\n### Fix\n\nThe 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.\n\n### Workarounds\n\n- Upgrade to the patched version.\n- Enable authentication (`CRAWL4AI_API_TOKEN`).\n- Restrict the container's outbound network access (egress firewall / no metadata route).\n\n### Credits\n\nInternal security audit (Crawl4AI maintainers).\n\n## Affected packages\n\n- `crawl4ai <= 0.8.7`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `crawl4ai 0.8.8`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}