CVE-2020-7790 in browsershot
Summary
by MITRE • 12/11/2020
This affects the package spatie/browsershot from 0.0.0. By specifying a URL in the file:// protocol an attacker is able to include arbitrary files in the resultant PDF.
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Analysis
by VulDB Data Team • 12/16/2020
The vulnerability identified as CVE-2020-7790 resides within the spatie/browsershot package, a popular PHP library that enables developers to generate PDFs and screenshots from web pages using headless Chrome or Chromium browsers. This security flaw represents a critical path traversal and arbitrary file inclusion vulnerability that can be exploited by malicious actors to access sensitive files on the server where the application is hosted. The vulnerability specifically affects versions of the package from 0.0.0 onwards, indicating that it has been present since the initial releases of this library.
The technical exploitation occurs through the manipulation of URL protocols within the browsershot library's functionality. When an attacker supplies a file:// protocol URL to the library, the system fails to properly validate or sanitize the input, allowing the library to process and include arbitrary local files in the generated PDF output. This flaw stems from insufficient input validation and improper handling of file system paths, creating a direct pathway for attackers to access files that should remain protected. The vulnerability operates at the intersection of insecure file handling and protocol misinterpretation, where the library's intended use case for web page rendering becomes a vector for local file disclosure.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially expose sensitive server resources including configuration files, database credentials, source code, and other confidential data. Attackers can leverage this vulnerability to gain unauthorized access to files that may contain authentication tokens, API keys, or other critical information that could lead to further system compromise. The vulnerability is particularly dangerous in environments where the browsershot library is used in applications handling sensitive data or where the application server has elevated privileges. This weakness can be exploited through various attack vectors including web application penetration testing, automated scanning tools, or direct exploitation of web applications that utilize the affected library.
Mitigation strategies for CVE-2020-7790 should focus on immediate version updates to the spatie/browsershot package, as the maintainers have likely released patches addressing this specific vulnerability. Organizations should implement comprehensive input validation measures that explicitly reject file:// protocol URLs or sanitize all inputs before processing them through the browsershot library. Network-level protections such as web application firewalls can help detect and block suspicious requests containing file protocol URLs. Additionally, system administrators should conduct thorough audits of all applications using this library to ensure proper implementation of security controls and remove unnecessary file access permissions for the application processes. This vulnerability aligns with CWE-22 Path Traversal and CWE-94 Code Injection categories, and can be mapped to ATT&CK techniques involving privilege escalation through file inclusion and credential access through information discovery. The recommended remediation includes not only updating the vulnerable component but also implementing principle of least privilege access controls and regular security assessments of third-party dependencies.