CVE-2017-6848 in PoDoFo
Summary
by MITRE
The PoDoFo::PdfXObject::PdfXObject function in PdfXObject.cpp in PoDoFo 0.9.5 allows remote attackers to cause a denial of service (NULL pointer dereference) via a crafted file.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability identified as CVE-2017-6848 resides within the PoDoFo library version 0.9.5, specifically in the PdfXObject::PdfXObject function located in the PdfXObject.cpp source file. This flaw represents a classic null pointer dereference issue that can be exploited by remote attackers to trigger a denial of service condition. The vulnerability manifests when the library processes maliciously crafted PDF files that contain malformed xobject structures, leading to a situation where the application attempts to access a null pointer during the object instantiation process.
The technical execution of this vulnerability follows a predictable pattern where an attacker crafts a PDF file containing specially constructed xobject elements that, when parsed by PoDoFo, result in uninitialized pointer variables being dereferenced. This type of vulnerability falls under CWE-476 which specifically addresses null pointer dereference conditions in software implementations. The flaw demonstrates poor input validation and error handling within the PDF parsing component, as the library fails to properly validate the structure and content of xobject elements before attempting to process them. The attack vector is remote and requires no authentication, making it particularly dangerous as it can be exploited through automated means against any system utilizing the vulnerable PoDoFo library.
From an operational impact perspective, this vulnerability creates significant risk for applications that rely on PoDoFo for PDF processing, including document management systems, web applications that handle PDF uploads, and any software that renders or manipulates PDF documents. The denial of service condition can lead to complete application unavailability, requiring system administrators to restart services or reboot affected systems to restore normal operation. This vulnerability can be particularly devastating in production environments where continuous availability is critical, as attackers can repeatedly exploit the flaw to maintain service disruption. The impact extends beyond simple service interruption, as it can also provide an avenue for more sophisticated attacks if the system is not properly isolated from malicious PDF content.
Mitigation strategies for CVE-2017-6848 should prioritize immediate patching of the PoDoFo library to version 0.9.6 or later, which contains the necessary fixes for the null pointer dereference issue. Organizations should implement comprehensive input validation measures that sanitize all PDF content before processing, including implementing strict file format validation and content scanning. Network-level defenses such as web application firewalls and content filtering systems can provide additional protection by blocking suspicious PDF files at the perimeter. The vulnerability also highlights the importance of implementing proper error handling and defensive programming practices, including null pointer checks and graceful degradation mechanisms. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to denial of service and privilege escalation, as it can be used to disrupt services and potentially create opportunities for further exploitation. System administrators should also consider implementing monitoring and alerting mechanisms to detect unusual patterns of service disruption that may indicate exploitation attempts.