CVE-2022-28368 in Dompdf
Summary
by MITRE • 04/03/2022
Dompdf 1.2.1 allows remote code execution via a .php file in the src:url field of an @font-face Cascading Style Sheets (CSS) statement (within an HTML input file).
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Analysis
by VulDB Data Team • 11/04/2024
The vulnerability identified as CVE-2022-28368 represents a critical remote code execution flaw in the dompdf library version 1.2.1, which is widely used for converting html documents to pdf format in web applications. This vulnerability specifically targets the processing of font declarations within css style sheets, creating a pathway for attackers to execute arbitrary code on systems running affected versions of the library. The flaw occurs when dompdf processes html input containing css @font-face declarations that reference external resources through the src:url field, allowing malicious actors to inject php code that gets executed during the pdf generation process.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within dompdf's css parsing mechanism. When the library encounters a css @font-face rule with a src:url declaration pointing to a remote resource, it fails to properly validate the url parameter, particularly when it contains php code or references to local files that could be exploited. This weakness directly maps to CWE-94, which describes improper control of generation of code, and CWE-77, which addresses improper neutralization of special elements used in a command or injection attack. The vulnerability allows attackers to craft malicious html documents containing specially formatted css declarations that, when processed by dompdf, result in code execution with the privileges of the web server process.
The operational impact of this vulnerability is severe and far-reaching across numerous web applications that utilize dompdf for document generation. Attackers can leverage this flaw to execute arbitrary php code on vulnerable systems, potentially leading to complete system compromise, data exfiltration, and persistence mechanisms. The vulnerability affects any application that accepts user-provided html content and processes it through dompdf, including content management systems, document management platforms, and web applications that generate pdf reports from user input. The remote nature of the exploitation means that attackers do not require local access to the target system, making this vulnerability particularly dangerous in multi-tenant environments or shared hosting scenarios. This vulnerability directly aligns with attack techniques described in the attack pattern taxonomy under the MITRE ATT&CK framework, specifically mapping to techniques involving code injection and remote command execution.
Organizations affected by this vulnerability should immediately implement multiple layers of mitigation strategies to protect their systems. The primary recommendation involves upgrading to dompdf version 1.2.2 or later, which contains the necessary patches to address the css parsing vulnerability. Additionally, administrators should implement strict input validation and sanitization for all html content that will be processed through dompdf, particularly focusing on css declarations and font references. Web application firewalls and input filtering mechanisms should be configured to detect and block suspicious css src:url patterns that may contain php code or other malicious content. Network segmentation and privilege separation should be implemented to limit the potential impact of successful exploitation, ensuring that web server processes operate with minimal required permissions. Regular security assessments and penetration testing should be conducted to identify other potential injection vectors and ensure that all dependencies are properly maintained and updated.