Vulnerability · Published Jun 23, 2026 · Assigned by GitHub_M
CVE-2026-53753Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API
Critical 9.8
In plain English
A critical-severity code injection in crawl4ai from unclecode. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 2.9% (higher than 87% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei, public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | crawl4ai | 0.8.7 | GHSA-qxjp-w3pj-48m7 |
| PyPI | crawl4ai | 0.8.7 | PYSEC-2026-319 |
Affected products (as reported)
Weakness: CWE-94, CWE-913 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://github.com/unclecode/crawl4ai/security/advisories/GHSA-qxjp-w3pj-48m7 x_refsource_CONFIRM