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CVE

CVE-2026-53753

9.8
CVSScritical
Exploitable remotely over the internet · no authentication required.
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.

Attack Vector
Network
Privileges Req.
None
User Interaction
None
crawl4ai
Updated Sep 18, 2026View on NVD →
S4E scanner

Crawl4AI <= 0.8.6 - Remote Code Execution

Crawl4AI through 0.8.6 ships a Docker API server that exposes an unauthenticated /crawl endpoint. The computed field type of JsonCssExtractionStrategy evaluates a user supplied expression inside an AST based sandbox that does not restrict attribute access on generator frame objects. A generator expression can therefore reach gi_frame.f_back, walk the caller chain to f_builtins, recover __import__ and execute arbitrary operating system commands as the user running the container. References: https://github.com/unclecode/crawl4ai/security/advisories/GHSA-qxjp-w3pj-48m7 https://github.com/unclecode/crawl4ai/pull/1855 https://github.com/unclecode/crawl4ai/pull/1886 https://github.com/pypa/advisory-database/tree/main/vulns/crawl4ai/PYSEC-2026-319.yaml https://nvd.nist.gov/vuln/detail/CVE-2026-53753 Remediation: Upgrade Crawl4AI to version 0.8.7 or later, where computed field expressions are disabled.

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CVE history: crawl4ai

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