CVE-2018-11256 in PoDoFo
Summary
by MITRE
An issue was discovered in PoDoFo 0.9.5. The function PdfDocument::Append() in PdfDocument.cpp in PoDoFo 0.9.5 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted PDF document.
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Analysis
by VulDB Data Team • 03/14/2023
The vulnerability identified as CVE-2018-11256 represents a critical denial of service weakness within the PoDoFo library version 0.9.5, specifically manifesting in the PdfDocument::Append() function located in PdfDocument.cpp. This flaw enables remote attackers to deliberately crash applications that utilize PoDoFo by crafting malicious PDF documents that trigger a NULL pointer dereference during document processing. The issue stems from inadequate input validation and error handling within the library's document appending mechanism, where the software fails to properly validate or sanitize incoming PDF data before attempting to process it. The vulnerability affects any application that integrates PoDoFo for PDF manipulation, particularly those that accept user-uploaded or externally sourced PDF files for appending operations.
The technical implementation of this vulnerability involves the PdfDocument::Append() function failing to perform proper null checks on pointer variables that are expected to contain valid document data structures. When a maliciously crafted PDF file is processed through this function, the library attempts to dereference a NULL pointer, leading to an application crash and subsequent denial of service condition. This behavior aligns with CWE-476 which categorizes NULL pointer dereference as a common software weakness that can result in application instability and potential system compromise. The vulnerability operates at the application layer and can be exploited without requiring any special privileges or authentication, making it particularly dangerous in environments where users can upload or process external PDF content.
From an operational perspective, this vulnerability creates significant risks for organizations relying on PoDoFo for PDF document handling, particularly in web applications, document management systems, and any service that processes user-generated PDF content. The impact extends beyond simple service interruption as it can be leveraged as a vector for more sophisticated attacks, potentially enabling attackers to disrupt critical business operations or serve as a stepping stone for further exploitation attempts. The vulnerability is particularly concerning in cloud-based document processing services or content management systems where multiple users may interact with the same PDF processing infrastructure, as a single malicious document can potentially affect the entire service availability.
Organizations utilizing PoDoFo 0.9.5 should immediately implement mitigations including upgrading to a patched version of the library where available, implementing input validation and sanitization measures before processing any external PDF content, and deploying network-level restrictions to limit PDF processing capabilities where possible. Additionally, implementing proper error handling and graceful degradation mechanisms can help prevent complete service crashes when encountering malformed PDF data. The ATT&CK framework categorizes this type of vulnerability under T1499 which covers network denial of service attacks, while the broader exploitation chain may involve techniques from T1059 for command execution and T1210 for exploitation of remote services. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other PDF processing libraries and document handling components within the organization's infrastructure.