CVE-2023-39062 in HTML2PDF
Summary
by MITRE • 08/28/2023
Cross Site Scripting vulnerability in Spipu HTML2PDF before v.5.2.8 allows a remote attacker to execute arbitrary code via a crafted script to the forms.php.
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Analysis
by VulDB Data Team • 09/22/2023
The CVE-2023-39062 vulnerability represents a critical cross site scripting flaw discovered in the Spipu HTML2PDF library prior to version 5.2.8. This vulnerability exists within the forms.php component of the library, which is commonly used for generating pdf documents from html content in web applications. The flaw allows remote attackers to inject malicious javascript code through crafted input parameters, potentially leading to unauthorized access and execution of arbitrary commands on affected systems. The vulnerability specifically affects applications that utilize the HTML2PDF library for document generation, making it particularly concerning for web applications that process user-provided content.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the forms.php script. When the library processes user-supplied data through the form handling functionality, it fails to properly sanitize or escape special characters that could be interpreted as executable javascript code. This weakness creates an environment where attackers can inject malicious payloads that execute in the context of the victim's browser when the generated pdf is viewed or processed. The vulnerability operates under CWE-79 which categorizes cross site scripting flaws as weaknesses that allow attackers to inject client-side scripts into web applications. The attack vector is particularly dangerous because it can be exploited through web forms that utilize the affected library, making it accessible to threat actors without requiring elevated privileges or complex exploitation techniques.
The operational impact of this vulnerability extends beyond simple script execution, as it can potentially lead to session hijacking, data theft, and further exploitation within the target environment. When an attacker successfully injects malicious code through the forms.php endpoint, they can manipulate the pdf generation process to include malicious javascript that executes in the user's browser context. This could result in unauthorized access to sensitive data, modification of application functionality, or redirection to malicious sites. The vulnerability's remote exploitability means that attackers do not need physical access to the target system, and can leverage the flaw from any location with network access to the vulnerable application. According to ATT&CK framework, this vulnerability maps to T1566 which covers social engineering techniques, specifically targeting the application layer through web-based attacks.
Organizations utilizing the Spipu HTML2PDF library should immediately implement mitigations to address this vulnerability. The primary recommendation involves upgrading to version 5.2.8 or later, which includes proper input validation and output encoding mechanisms to prevent malicious script injection. Additionally, implementing proper input sanitization at the application level, including the use of Content Security Policy headers, can provide defense-in-depth measures against exploitation attempts. Organizations should also consider implementing web application firewalls that can detect and block suspicious input patterns targeting the forms.php endpoint. The vulnerability demonstrates the critical importance of proper input validation in web applications, as highlighted by the CWE-79 classification which emphasizes the need for robust sanitization of user inputs. Regular security assessments and code reviews should be conducted to identify similar vulnerabilities in other components of the application stack, ensuring comprehensive protection against similar attack vectors.