CVE-2026-53753
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (2.90%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 10.0 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 2.90% probability · 86th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-94, CWE-913
- Affected
- kidocode/crawl4ai
- Source
- security-advisories@github.com
References
- https://github.com/unclecode/crawl4ai/security/advisories/GHSA-qxjp-w3pj-48m7Third Party Advisory, Mitigation
- https://github.com/unclecode/crawl4ai/security/advisories/GHSA-qxjp-w3pj-48m7Third Party Advisory, Mitigation
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.