Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain – Pre-Auth RCE in Docker API_CVE-2026-53753

{
    "lastseen": "",
    "description": "Crawl4AI is an open-source LLM friendly web crawler & scraper. Prior to 0.8.7, the _safe_eval_expression() function in the computed fields feature uses an AST validator that only blocks attributes starting with underscore. Python generator and frame object attributes (gi_frame, f_back, f_builtins) do NOT start with underscore, enabling a complete sandbox escape to achieve arbitrary code execution. The attack requires no authentication (JWT disabled by default) and is triggered via POST /crawl with a crafted extraction schema. This vulnerability is fixed in 0.8.7.",
    "published": "2026-06-23T18:17:18.936Z",
    "modified": "2026-06-23T18:55:22.278Z",
    "type": "cve",
    "title": "Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API",
    "source": "GitHub_M",
    "references": "https://github.com/unclecode/crawl4ai/security/advisories/GHSA-qxjp-w3pj-48m7",
    "id": "CVE-2026-53753",
    "bulletinFamily": "",
    "cwe": [
        "CWE-94",
        "CWE-913"
    ],
    "cvelist": null,
    "sourceData": "unclecode crawl4ai < 0.8.7",
    "sourceHref": "",
    "cvss": {
        "score": 9.8,
        "severity": "CRITICAL",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "crawl4ai",
    "version": "< 0.8.7",
    "vendor": "unclecode",
    "ai_description": "AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API",
    "ai_severity": "Critical",
    "ai_vendor": "unclecode",
    "ai_product": "Crawl4AI",
    "ai_version": "< 0.8.7",
    "ai_score": 9.8
}