CVE-2017-7994 in PoDoFo
Summary
by MITRE
The function TextExtractor::ExtractText in TextExtractor.cpp:77 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 • 04/22/2017
The vulnerability identified as CVE-2017-7994 resides within the PoDoFo library version 0.9.5, specifically within the TextExtractor::ExtractText function located in TextExtractor.cpp at line 77. This flaw represents a classic null pointer dereference issue that can be exploited by remote attackers through the careful crafting of malicious PDF documents. The PoDoFo library serves as a widely-used open-source library for creating and modifying PDF files, making this vulnerability particularly concerning for applications that process untrusted PDF content. The vulnerability classification aligns with CWE-476 which describes null pointer dereference conditions that can lead to application crashes and potential denial of service scenarios. When a maliciously constructed PDF document is processed by an application utilizing the vulnerable PoDoFo library, the TextExtractor::ExtractText function attempts to dereference a null pointer, resulting in an immediate application crash and subsequent denial of service condition.
The technical exploitation of this vulnerability requires an attacker to craft a specific PDF document that triggers the null pointer dereference within the text extraction routine. This occurs when the function processes PDF content where certain text objects or formatting elements are improperly structured, leading to a scenario where a pointer that should contain a valid memory reference instead holds a null value. The application crashes immediately upon attempting to access this null pointer, effectively rendering the service unavailable to legitimate users. The attack vector is remote and does not require user interaction, making it particularly dangerous in automated attack scenarios. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1499.004 which involves network denial of service attacks that target application availability through exploitation of software flaws. The impact is limited to denial of service but can be highly disruptive in environments where PDF processing is critical to business operations.
The operational impact of CVE-2017-7994 extends beyond simple application crashes to encompass broader service availability concerns for systems that rely on PoDoFo for PDF processing capabilities. Organizations utilizing applications such as document management systems, web portals, or automated processing services that depend on PoDoFo may experience significant disruption when this vulnerability is exploited. The vulnerability affects not only standalone applications but also web applications that process user-uploaded PDF files, creating potential attack surfaces for malicious actors seeking to disrupt service availability. The exploitability of this vulnerability is relatively straightforward, requiring only the creation of a specific PDF file structure that triggers the null pointer dereference condition. Organizations should consider implementing input validation and sanitization measures to mitigate the risk, although the most effective approach remains updating to a patched version of the PoDoFo library. The vulnerability also highlights the importance of proper error handling and null pointer validation in library code, as this flaw could potentially be leveraged in more sophisticated attacks if combined with other vulnerabilities in the processing pipeline. This issue demonstrates the critical need for thorough testing of third-party libraries and the implementation of robust security practices in software development lifecycle processes.