CVE-2026-53753: CWE-94: Improper Control of Generation of Code ('Code Injection') in unclecode crawl4ai
CVE-2026-53753 is a critical code injection vulnerability in the open-source web crawler crawl4ai prior to version 0.8.7. The vulnerability arises from improper control in the _safe_eval_expression() function, which uses an AST validator that only blocks attributes starting with an underscore. This allows attackers to exploit Python generator and frame object attributes that do not start with an underscore to escape the sandbox and execute arbitrary code. The attack requires no authentication and is triggered via a crafted POST request to the /crawl endpoint. The vulnerability is fixed in version 0.8.7.
AI Analysis
Technical Summary
In crawl4ai versions before 0.8.7, the computed fields feature's _safe_eval_expression() function inadequately restricts code execution by only blocking attribute access starting with underscores. Python internal attributes such as gi_frame, f_back, and f_builtins, which do not start with underscores, can be leveraged to bypass this restriction, enabling a complete sandbox escape and arbitrary code execution. This vulnerability can be exploited without authentication by sending a specially crafted extraction schema in a POST request to the /crawl endpoint. The issue is resolved in crawl4ai version 0.8.7.
Potential Impact
Successful exploitation allows unauthenticated attackers to execute arbitrary code on the affected system, leading to full compromise of confidentiality, integrity, and availability. This includes potential unauthorized access, data manipulation, and service disruption.
Mitigation Recommendations
Upgrade crawl4ai to version 0.8.7 or later, where this vulnerability is fixed. No other mitigations are indicated or required as the fix addresses the root cause.
CVE-2026-53753: CWE-94: Improper Control of Generation of Code ('Code Injection') in unclecode crawl4ai
Description
CVE-2026-53753 is a critical code injection vulnerability in the open-source web crawler crawl4ai prior to version 0.8.7. The vulnerability arises from improper control in the _safe_eval_expression() function, which uses an AST validator that only blocks attributes starting with an underscore. This allows attackers to exploit Python generator and frame object attributes that do not start with an underscore to escape the sandbox and execute arbitrary code. The attack requires no authentication and is triggered via a crafted POST request to the /crawl endpoint. The vulnerability is fixed in version 0.8.7.
CVSS v3.1
Score 9.8critical
Affected software
pkg:github/unclecode/crawl4aiRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
In crawl4ai versions before 0.8.7, the computed fields feature's _safe_eval_expression() function inadequately restricts code execution by only blocking attribute access starting with underscores. Python internal attributes such as gi_frame, f_back, and f_builtins, which do not start with underscores, can be leveraged to bypass this restriction, enabling a complete sandbox escape and arbitrary code execution. This vulnerability can be exploited without authentication by sending a specially crafted extraction schema in a POST request to the /crawl endpoint. The issue is resolved in crawl4ai version 0.8.7.
Potential Impact
Successful exploitation allows unauthenticated attackers to execute arbitrary code on the affected system, leading to full compromise of confidentiality, integrity, and availability. This includes potential unauthorized access, data manipulation, and service disruption.
Mitigation Recommendations
Upgrade crawl4ai to version 0.8.7 or later, where this vulnerability is fixed. No other mitigations are indicated or required as the fix addresses the root cause.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-10T17:48:40.546Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a3ad655eed863c81e79458b
Added to database: 06/23/2026, 18:54:13 UTC
Last enriched: 06/23/2026, 19:10:09 UTC
Last updated: 06/23/2026, 21:58:02 UTC
Views: 6
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