CVE-2026-53753CWE-913CWE-94

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

Critical · published June 23, 2026

CVSS v3.1
9.8
EPSS
3%
Percentile
86.9
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
9.8 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.02900 · 86.9th percentile
Weaknesses
CWE-913 · Improper Control of Dynamically-Managed Code Resources; CWE-94 · Improper Control of Generation of Code ('Code Injection')
Published
2026-06-23T18:17Z
EPSS history
Timeline
  • 23 JUN 18:17Z
    Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API
    cvelistv5