Detect Crawl4AI AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Google Chronicle
Detects exploitation of CVE-2026-53753, a critical pre-authentication remote code execution vulnerability in Crawl4AI (<=0.8.6) Docker API. The vulnerability allows attackers to escape Python AST-based sandboxing via generator frame introspection (gi_frame.f_back chain), enabling arbitrary code execution without authentication. CVSS 9.8 critical; public PoC available.
MITRE ATT&CK
YARA-L Detection Query
rule crawl4ai_sandbox_escape_cve_2026_53753 {
meta:
author = "df00tech"
description = "Detects CVE-2026-53753 Crawl4AI AST sandbox escape via gi_frame.f_back chain"
severity = "CRITICAL"
priority = "HIGH"
reference = "https://github.com/advisories/GHSA-qxjp-w3pj-48m7"
events:
$http.metadata.event_type = "NETWORK_HTTP"
$http.target.port in (11235, 8080, 8000)
re.regex($http.target.url, `/(execute|run|crawl|extract)`)
$http.principal.ip = $src_ip
$proc.metadata.event_type = "PROCESS_LAUNCH"
$proc.principal.process.command_line = /gi_frame|f_back|__globals__|__builtins__|os\.system|__import__|subprocess/
$proc.principal.hostname = $host
match:
$src_ip over 5m
outcome:
$risk_score = 95
$alert_name = "CVE-2026-53753: Crawl4AI Pre-Auth RCE via AST Sandbox Escape"
condition:
$http and $proc
}Chronicle YARA-L rule detecting Crawl4AI API endpoint access correlated with Python process launch events containing AST sandbox escape patterns within a 5-minute window.
Data Sources
Required Tables
False Positives & Tuning
- Authorized security testing against Crawl4AI deployments in isolated environments
- Python applications that legitimately use generator frame inspection for profiling
- CI/CD pipelines that run Crawl4AI integration tests with dynamic code features
- Development instances where frame-level debugging is enabled
Other platforms for CVE-2026-53753
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1CVE-2026-53753 Basic Sandbox Escape via gi_frame
Expected signal: HTTP POST to /execute endpoint followed by Python process executing os.system('id') and writing to /tmp/crawl4ai_pwned.txt; child process of uvicorn/gunicorn spawning /bin/sh
- Test 2CVE-2026-53753 Remote Code Execution with Reverse Shell
Expected signal: Outbound TCP connection from Crawl4AI container to attacker IP on port 4444; subprocess.Popen spawning bash with stdin redirected to network socket
- Test 3CVE-2026-53753 Credential Exfiltration from Container Environment
Expected signal: HTTP POST with gi_frame payload followed by Python reading os.environ; response containing environment variable key-value pairs potentially including API_KEY, DATABASE_URL, VAULT_TOKEN
- Test 4CVE-2026-53753 Unauthenticated Version Fingerprinting
Expected signal: Unauthenticated HTTP GET to /health or root endpoint returning Crawl4AI version information without requiring credentials
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