---
title: "CVE-2026-53753: Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API"
url: https://erroneo.us/security/cve/CVE-2026-53753/
description: "CVE-2026-53753 (crawl4ai (PyPI)): Crawl4AI is an open-source LLM friendly web crawler & scraper. Prior to 0.8.7, the safeevalexpression() function in the…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-06-23
date_modified: 2026-07-20
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-53753"
kev: false
cvss: 9.8
epss: 0.029
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 2.9% , percentile 87: FIRST’s model estimates a 2.9% chance of exploitation activity in the next 30 days, higher than 87% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes crawl4ai (PyPI) <= 0.8.6, fixed in 0.8.7 . Check your lockfile, including transitive dependencies.

## What it is

Crawl4AI is an open-source LLM friendly web crawler & scraper. Prior to 0.8.7, the safeevalexpression() function in the computed fields feature uses an AST validator that only blocks attributes starting with underscore. Python generator and frame object attributes (giframe, fback, fbuiltins) 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

- PyPI `crawl4ai` <= 0.8.6 → fixed: 0.8.7

## Affected products (CVE record)

- unclecode crawl4ai: < 0.8.7

## Severity

- GitHub_M CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 2.90% probability of exploitation activity in the next 30 days; percentile 87.

## Sources

- [GitHub Advisory GHSA-qxjp-w3pj-48m7](https://github.com/advisories/GHSA-qxjp-w3pj-48m7)
- [CVE.org record CVE-2026-53753](https://www.cve.org/CVERecord?id=CVE-2026-53753)
- [NVD entry CVE-2026-53753](https://nvd.nist.gov/vuln/detail/CVE-2026-53753)
- [github.com](https://github.com/unclecode/crawl4ai/security/advisories/GHSA-qxjp-w3pj-48m7)
- [github.com](https://github.com/unclecode/crawl4ai/pull/1855)
- [github.com](https://github.com/unclecode/crawl4ai/pull/1886)
- [github.com](https://github.com/pypa/advisory-database/tree/main/vulns/crawl4ai/PYSEC-2026-319.yaml)
- [github.com](https://github.com/unclecode/crawl4ai)
- [pypi.org](https://pypi.org/project/crawl4ai)

---
Source page: https://erroneo.us/security/cve/CVE-2026-53753/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt