{"id":"GHSA-4qqr-vv2q-cmr5","summary":"Crawl4AI: SSRF filter bypass in Docker server via IPv6 transition forms (NAT64 / 6to4 / unspecified / v4-mapped)","details":"### 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).","aliases":["CVE-2026-53754","PYSEC-2026-587"],"modified":"2026-07-20T21:30:31.718896853Z","published":"2026-06-16T21:00:04Z","database_specific":{"nvd_published_at":"2026-06-23T19:17:07Z","cwe_ids":["CWE-918"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-06-16T21:00:04Z"},"references":[{"type":"WEB","url":"https://github.com/unclecode/crawl4ai/security/advisories/GHSA-4qqr-vv2q-cmr5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53754"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/crawl4ai/PYSEC-2026-587.yaml"},{"type":"PACKAGE","url":"https://github.com/unclecode/crawl4ai"}],"affected":[{"package":{"name":"crawl4ai","ecosystem":"PyPI","purl":"pkg:pypi/crawl4ai"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.8.8"}]}],"versions":["0.3.0","0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.3.6","0.3.7","0.3.71","0.3.72","0.3.73","0.3.731","0.3.74","0.3.741","0.3.742","0.3.743","0.3.744","0.3.745","0.3.746","0.3.8","0.4.0","0.4.1","0.4.21","0.4.22","0.4.23","0.4.24","0.4.241","0.4.242","0.4.243","0.4.244","0.4.245","0.4.246","0.4.247","0.4.248","0.4.248b3","0.4.3b1","0.4.3b2","0.4.3b3","0.5.0","0.5.0.post1","0.5.0.post2","0.5.0.post3","0.5.0.post4","0.5.0.post5","0.5.0.post6","0.5.0.post7","0.5.0.post8","0.6.0","0.6.0rc1","0.6.1","0.6.2","0.6.3","0.7.0","0.7.1","0.7.2","0.7.3","0.7.4","0.7.5","0.7.6","0.7.7","0.7.8","0.8.0","0.8.5","0.8.6","0.8.7"],"database_specific":{"last_known_affected_version_range":"\u003c= 0.8.7","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-4qqr-vv2q-cmr5/GHSA-4qqr-vv2q-cmr5.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"}]}