CVE-2017-6846 in PoDoFo
Summary
by MITRE
The GraphicsStack::TGraphicsStackElement::SetNonStrokingColorSpace function in graphicsstack.h in PoDoFo 0.9.4 allows remote attackers to cause a denial of service (NULL pointer dereference) via a crafted file.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/09/2020
The vulnerability identified as CVE-2017-6846 resides within the PoDoFo library version 0.9.4, specifically within the GraphicsStack::TGraphicsStackElement::SetNonStrokingColorSpace function located in graphicsstack.h. This flaw represents a classic null pointer dereference vulnerability that can be exploited by remote attackers through the careful crafting of malicious PDF files. The PoDoFo library serves as a popular open-source PDF processing library used in various applications for PDF creation, modification, and rendering, making this vulnerability particularly concerning for systems that handle untrusted PDF content.
The technical exploitation of this vulnerability occurs when a crafted PDF file contains malformed color space specifications that trigger a null pointer dereference during the processing of non-stroking color space operations. When the SetNonStrokingColorSpace function attempts to access a null pointer reference within the graphics stack element structure, the application crashes with a segmentation fault or access violation. This behavior aligns with CWE-476, which categorizes null pointer dereference as a common weakness that can lead to denial of service conditions. The vulnerability specifically manifests in the context of PDF parsing and graphics rendering operations where color space information is processed during document interpretation.
The operational impact of CVE-2017-6846 extends beyond simple application crashes, as it can be leveraged for broader denial of service attacks against systems that rely on PoDoFo for PDF processing. Attackers can craft malicious PDF documents that, when opened or processed by vulnerable applications, will cause the target system to crash or become unresponsive. This vulnerability affects any software that utilizes PoDoFo 0.9.4 for PDF handling, including web applications, document management systems, and PDF viewers. The remote nature of the attack means that exploitation can occur without requiring local access to the target system, making it particularly dangerous in web-facing applications where users might unknowingly download and process malicious PDF content.
Mitigation strategies for this vulnerability primarily involve upgrading to a patched version of the PoDoFo library where the null pointer dereference has been addressed through proper input validation and pointer checking. Organizations should also implement defensive measures such as validating PDF content before processing, employing sandboxing techniques for PDF handling, and utilizing intrusion detection systems to monitor for exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to the T1203 technique related to legitimate credentials and T1499 related to network denial of service, as it can be used to disrupt services by causing application crashes. Additionally, implementing proper error handling and input validation mechanisms within applications that use PoDoFo can provide additional defense in depth against similar vulnerabilities that may exist in other components of the PDF processing pipeline.