unclecode crawl4ai up to 0.8.6 Computed Fields Feature _safe_eval_expression code injection

Summaryinfo

A vulnerability was found in unclecode crawl4ai up to 0.8.6. It has been classified as critical. This issue affects the function _safe_eval_expression of the component Computed Fields Feature. This manipulation causes code injection. This vulnerability is tracked as CVE-2026-53753. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in unclecode crawl4ai up to 0.8.6 and classified as critical. Affected by this vulnerability is the function _safe_eval_expression of the component Computed Fields Feature. The manipulation with an unknown input leads to a code injection vulnerability. The CWE definition for the vulnerability is CWE-94. The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-53753 since 06/10/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059 for this issue.

Upgrading to version 0.8.7 eliminates this vulnerability.

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Productinfo

Vendor

• unclecode

Name

• crawl4ai

Version

• 0.8.0
• 0.8.1
• 0.8.2
• 0.8.3
• 0.8.4
• 0.8.5
• 0.8.6

Website

• Product: https://github.com/unclecode/crawl4ai/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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