{"id":"CVE-2026-53754","aliases":["GHSA-4qqr-vv2q-cmr5","PYSEC-2026-587"],"url":"https://o3.security/vulnerability/CVE-2026-53754","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).","published":"2026-06-23T18:16:34.260Z","modified":"2026-08-12T03:51:37.753745567Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"epss":{"score":0.00433,"percentile":0.36182,"asOf":"2026-09-01"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"crawl4ai","fixedVersion":"0.8.8"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53754.json"},{"type":"ADVISORY","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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:37.753745567Z"}}