CVE-2024-21549 in browsershot
Summary
by MITRE • 12/20/2024
Versions of the package spatie/browsershot before 5.0.3 are vulnerable to Improper Input Validation due to improper URL validation in the setUrl method. An attacker can exploit this vulnerability by utilizing view-source:file://, which allows for arbitrary file reading on a local file.
**Note:**
This is a bypass of the fix for [CVE-2024-21544](https://security.snyk.io/vuln/SNYK-PHP-SPATIEBROWSERSHOT-8496745).
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Analysis
by VulDB Data Team • 08/06/2026
The vulnerability identified as CVE-2024-21549 affects the spatie/browsershot package versions prior to 5.0.3, representing a critical improper input validation flaw that undermines the security of web applications relying on this library. This issue specifically manifests through the setUrl method which fails to properly validate URL inputs, creating a pathway for malicious actors to exploit the system. The vulnerability operates by leveraging the view-source:file:// protocol extension, which is a legitimate browser feature designed to display the source code of local files, but when misused through this library can enable unauthorized file access. The flaw represents a direct bypass of the previous fix implemented for CVE-2024-21544, indicating that the remediation efforts were insufficient to fully address the underlying validation mechanism. The security implications are particularly severe as this vulnerability allows for arbitrary file reading on the local system where the application is running, potentially exposing sensitive data, configuration files, and other system resources that should remain protected from unauthorized access.
The technical implementation of this vulnerability stems from inadequate sanitization of URL parameters within the browsershot library's core functionality. When developers pass user-supplied URLs to the setUrl method without proper validation, the library accepts inputs containing the view-source:file:// prefix without sufficient checks. This particular protocol prefix is designed to retrieve and display the source of local files, but in the context of this vulnerability, attackers can manipulate it to access files anywhere within the filesystem where the web application has read permissions. The flaw operates at the input validation layer, where CWE-20 - Improper Input Validation is the underlying weakness, as the system fails to properly validate or sanitize the URL input before processing it. This type of vulnerability falls under the ATT&CK technique T1059.007 - Command and Scripting Interpreter: Python, as it involves manipulating input to execute unintended file access operations, and T1566.001 - Phishing: Spearphishing Attachment, where malicious actors could craft URLs that exploit this vulnerability when users interact with them.
The operational impact of CVE-2024-21549 extends beyond simple data exposure, as it can lead to complete system compromise when combined with other vulnerabilities or attack vectors. An attacker exploiting this vulnerability can potentially read system configuration files, database credentials, application secrets, and other sensitive information stored on the local filesystem. The vulnerability is particularly dangerous in environments where the browsershot library is used to process user input from web forms or API endpoints, as it transforms legitimate browser automation functionality into a weapon for unauthorized file access. The bypass of the previous CVE-2024-21544 fix indicates a pattern of insufficient validation logic that may require more comprehensive input sanitization approaches. Organizations using affected versions of spatie/browsershot should immediately consider the potential for privilege escalation and lateral movement within their network infrastructure, as the ability to read arbitrary files can provide attackers with information needed to plan further attacks. The vulnerability affects not only the immediate file system access but also represents a broader concern about the security posture of applications that rely on browser automation libraries for content rendering and processing.
The recommended mitigation strategies for CVE-2024-21549 involve immediate version upgrading to spatie/browsershot 5.0.3 or later, which contains the proper input validation fixes. System administrators should implement comprehensive input sanitization at multiple layers, including application-level validation of all URL parameters passed to the browsershot library. Organizations should also consider implementing network-level restrictions to prevent access to sensitive file paths and implement proper access controls for the web application's file system permissions. The fix addresses the core validation issue by ensuring that URLs containing file:// protocols are properly sanitized or rejected, preventing the exploitation of the view-source:file:// bypass mechanism. Additionally, implementing web application firewalls and input validation rules that specifically block or sanitize URLs containing potentially dangerous protocol prefixes can provide additional defense in depth. Security monitoring should be enhanced to detect unusual file access patterns that might indicate exploitation attempts, and regular security assessments should be conducted to ensure that similar vulnerabilities are not present in other components of the application stack. The remediation process should also include a thorough review of all applications using this library to ensure that proper input validation is implemented throughout the codebase, and that no other similar vulnerabilities exist in related components.