CVE-2026-53753 Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API
Attackers can achieve remote code execution via sandbox escape in Crawl4AI's AST validator, requiring no authentication.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53753?
CVE-2026-53753 is a critical code injection vulnerability in unclecode crawl4ai, published on 23 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-53753?
3 open source packages ship an affected version, including crawl4ai. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
crawl4ai PyPI | All versions | 0.8.7 |
crawl4ai PyPI | All versions | 0.8.7 |
crawl4ai PyPI | All versions | 0.8.7 |
Products include Kidocode Crawl4ai.
How do I fix CVE-2026-53753?
Upgrade crawl4ai to 0.8.7 or later.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-53753 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53753 exists.
Public exploit code: 1 Nuclei template and 2 proofs of concept on GitHub.
Other vulnerabilities in unclecode crawl4ai
- CVE-2026-57572 Crawl4AI: Unauthenticated RCE via Chromium launch-argument injection in browser_config.extra_args
- CVE-2026-26216 Crawl4AI < 0.8.0 Docker API Unauthenticated Remote Code Execution via Hooks Parameter
- CVE-2026-57571 Crawl4AI arbitrary file write via download filename path traversal
- CVE-2026-56265 Crawl4AI - Authentication Bypass via Hardcoded JWT Signing Key
- CVE-2026-56261 Crawl4AI - Server-Side Request Forgery via Webhook URLs
Sources
Also known as GHSA-qxjp-w3pj-48m7, PYSEC-2026-319.