CVE-2015-8868 in Poppler
Summary
by MITRE
Heap-based buffer overflow in the ExponentialFunction::ExponentialFunction function in Poppler before 0.40.0 allows remote attackers to cause a denial of service (memory corruption and crash) or possibly execute arbitrary code via an invalid blend mode in the ExtGState dictionary in a crafted PDF document.
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Analysis
by VulDB Data Team • 07/29/2022
The vulnerability identified as CVE-2015-8868 represents a critical heap-based buffer overflow within the Poppler PDF rendering library, specifically affecting versions prior to 0.40.0. This flaw resides in the ExponentialFunction::ExponentialFunction function, which processes exponential functions during PDF document parsing. The vulnerability manifests when processing malformed PDF documents containing invalid blend modes within the ExtGState dictionary, a component used to define extended graphics state parameters in PDF files. The flaw constitutes a classic buffer overflow scenario where insufficient bounds checking allows malicious data to overwrite adjacent memory locations, potentially leading to system instability or unauthorized code execution.
The technical exploitation of this vulnerability requires an attacker to craft a malicious PDF document containing malformed blend mode specifications within the ExtGState dictionary. When a vulnerable Poppler-based application processes this document, the ExponentialFunction::ExponentialFunction routine fails to properly validate input parameters, leading to memory corruption. This memory corruption occurs in the heap memory region where the function allocates buffers for processing exponential functions, creating conditions where attacker-controlled data can overwrite critical memory structures. The vulnerability's impact extends beyond simple denial of service, as the memory corruption can potentially be leveraged for arbitrary code execution depending on memory layout and exploitation circumstances. The flaw aligns with CWE-121, heap-based buffer overflow, and represents a common class of vulnerabilities in PDF rendering engines where improper input validation leads to memory corruption.
The operational impact of CVE-2015-8868 is significant for organizations relying on Poppler-based PDF processing systems, including web browsers, document viewers, and content management systems. Applications such as Evince, Okular, and various web-based PDF viewers that utilize Poppler as their underlying rendering engine are at risk when processing untrusted PDF content. The vulnerability can be exploited remotely through web-based attacks, email attachments, or any scenario where users might encounter malicious PDF documents. This makes it particularly dangerous in enterprise environments where users frequently interact with PDF content from external sources. The potential for remote code execution escalates the risk level, as successful exploitation could allow attackers to gain control over affected systems. According to ATT&CK framework, this vulnerability maps to T1059.007 for remote code execution and T1203 for exploitation of remote services, making it a valuable target for attackers seeking persistent access to compromised systems.
Mitigation strategies for CVE-2015-8868 primarily focus on immediate version upgrades to Poppler 0.40.0 or later, which contain patches addressing the buffer overflow condition. System administrators should prioritize patch management across all affected applications and services that utilize Poppler for PDF processing. Additional protective measures include implementing PDF sandboxing techniques, deploying content filtering solutions that scan PDF documents for suspicious structures, and configuring applications to disable processing of untrusted PDF content when possible. Network-level protections such as web application firewalls can help detect and block malicious PDF content before it reaches end-user systems. Organizations should also consider implementing least privilege principles for PDF processing applications, limiting their access to system resources and preventing potential privilege escalation through successful exploitation. The vulnerability serves as a reminder of the critical importance of input validation in graphics processing libraries and the need for comprehensive security testing of document rendering components against malformed inputs.