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CVE-2026-53753— Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API

Quick assessment

Affected
unclecode crawl4ai
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

UncleCode Crawl4AI是新加坡UncleCode个人开发者的一款AI驱动的爬虫软件。 UncleCode Crawl4AI 0.8.7之前版本存在安全漏洞，该漏洞源于_safe_eval_expression()函数中的AST验证器仅阻止以下划线开头的属性，导致可以通过Python生成器和帧对象属性实现沙箱逃逸，造成任意代码执行。

CVSS 9.8 · Critical EPSS 2.90% · P87

Public Exploits 1

Nuclei · 1 CVE-2026-53753.yaml [template]

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
unclecode crawl4ai < 0.8.7 affected
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I. Basic Information for CVE-2026-53753

Vulnerability Information
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Vulnerability Title
Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对生成代码的控制不恰当(代码注入)
Source: CVE Program / CVE List V5
Vulnerability Title
UncleCode Crawl4AI 处理逻辑错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
UncleCode Crawl4AI是新加坡UncleCode个人开发者的一款AI驱动的爬虫软件。 UncleCode Crawl4AI 0.8.7之前版本存在安全漏洞，该漏洞源于_safe_eval_expression()函数中的AST验证器仅阻止以下划线开头的属性，导致可以通过Python生成器和帧对象属性实现沙箱逃逸，造成任意代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
unclecode crawl4ai < 0.8.7 -

II. Public POCs for CVE-2026-53753

# POC Description Source Link Shenlong Link
1 Crawl4AI through 0.8.6 ships a Docker API server that exposes an unauthenticated /crawl endpoint. The computed field type of JsonCssExtractionStrategy evaluates a user supplied expression inside an AST based sandbox that does not restrict attribute access on generator frame objects. A generator expression can therefore reach gi_frame.f_back, walk the caller chain to f_builtins, recover __import__ and execute arbitrary operating system commands as the user running the container. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-53753.yaml POC Details
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Qwen3.6-35B-A3B · 8754 chars
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III. Intelligence Information for CVE-2026-53753

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Vendor Advisories for CVE-2026-53753 (1)

Same Patch Batch · unclecode · 2026-06-23 · 3 CVEs total

CVE-2026-53755 8.6 HIGH Crawl4AI: SSRF via proxy settings in the Docker server bypasses the crawl-URL SSRF check
CVE-2026-53754 7.5 HIGH Crawl4AI: SSRF filter bypass in Docker server via IPv6 transition forms (NAT64 / 6to4 / un

IV. Related Vulnerabilities

Same product: crawl4ai
Same vendor: unclecode
Same weakness: CWE-94