CVE-2017-7235 in cloudflare-scrape
Summary
by MITRE
An issue was discovered in cloudflare-scrape 1.6.6 through 1.7.1. A malicious website owner could craft a page that executes arbitrary Python code against any cfscrape user who scrapes that website. This is fixed in 1.8.0.
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Analysis
by VulDB Data Team • 11/14/2022
The vulnerability identified as CVE-2017-7235 represents a critical code execution flaw in the cloudflare-scrape library version 1.6.6 through 1.7.1. This issue arises from the library's improper handling of Cloudflare's anti-bot protection mechanisms, specifically when processing JavaScript challenges that Cloudflare employs to distinguish between human users and automated scripts. The flaw enables attackers to inject malicious code that executes within the context of any user who employs the affected version of cfscrape to scrape content from compromised websites.
The technical root cause stems from the library's interpretation and execution of JavaScript code generated by Cloudflare's challenge pages. When cfscrape encounters a Cloudflare-protected page, it must execute JavaScript to bypass the anti-bot measures and obtain access to the original content. However, in the vulnerable versions, the library fails to properly sanitize or validate the JavaScript code received from Cloudflare, allowing attackers to inject malicious payloads that get executed during the scraping process. This represents a classic server-side request forgery vulnerability combined with a code injection flaw, where the attacker crafts a webpage that, when processed by the vulnerable cfscrape library, executes arbitrary Python code on the victim's machine.
The operational impact of this vulnerability extends far beyond simple data theft, as it enables complete compromise of systems running vulnerable versions of cfscrape. Any developer or automated system that uses this library to scrape websites protected by Cloudflare becomes a potential target for remote code execution attacks. The attack vector is particularly insidious because it requires no direct interaction with the target system beyond crafting a malicious webpage, and the exploitation occurs automatically when legitimate scraping operations are performed. This vulnerability aligns with CWE-94, which describes improper control of generation of code, and specifically manifests as a code injection vulnerability where attacker-controlled input is executed as code.
Organizations and developers utilizing cfscrape for web scraping operations face significant risk exposure with this vulnerability, as it essentially transforms legitimate scraping tools into potential attack vectors. The fix implemented in version 1.8.0 addresses this by implementing proper input validation and sanitization of JavaScript code received from Cloudflare challenge pages, ensuring that only expected and safe code execution occurs. System administrators and security teams should immediately upgrade to version 1.8.0 or later and audit any existing systems that may be running vulnerable versions. The vulnerability also demonstrates the importance of proper sandboxing and code validation in web scraping libraries, particularly those that must execute dynamic JavaScript content to bypass anti-bot protections. This issue highlights the broader security implications of automated scraping tools and their potential as attack vectors in modern web security landscapes, aligning with ATT&CK technique T1059.006 for execution through scripting and T1213.002 for data from information repositories.