CVE-2017-14976 in Poppler
Summary
by MITRE
The FoFiType1C::convertToType0 function in FoFiType1C.cc in Poppler 0.59.0 has a heap-based buffer over-read vulnerability if an out-of-bounds font dictionary index is encountered, which allows an attacker to launch a denial of service attack.
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Analysis
by VulDB Data Team • 12/30/2022
The vulnerability identified as CVE-2017-14976 resides within the Poppler PDF rendering library version 0.59.0, specifically in the FoFiType1C.cc source file where the FoFiType1C::convertToType0 function exhibits heap-based buffer over-read behavior. This flaw occurs when processing PostScript Type1C font data within PDF documents, creating a critical security concern that can be exploited by malicious actors. The vulnerability stems from insufficient bounds checking during font dictionary index validation, allowing an attacker to craft specially malformed PDF files that trigger the over-read condition when the library attempts to process out-of-bounds font indices. The technical implementation involves the function's failure to properly validate array access boundaries when converting Type1C fonts to Type0 format, resulting in memory access beyond allocated buffer limits. This vulnerability falls under CWE-125, which specifically addresses out-of-bounds read conditions, and represents a classic example of memory safety issues that can lead to system instability and denial of service attacks.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged in broader attack scenarios within PDF processing environments. When exploited, the heap-based buffer over-read can cause the Poppler library to crash or behave unpredictably, potentially leading to application termination or system instability in environments where PDF rendering is critical. This vulnerability affects any system or application that relies on Poppler for PDF processing, including web browsers, document viewers, and server-side PDF handling systems. The attack vector requires an attacker to craft a malicious PDF document containing malformed Type1C font data with invalid dictionary indices, making it particularly dangerous in environments where users might encounter untrusted PDF content. The vulnerability's exploitation does not typically require complex privileges or specialized conditions, as it can be triggered through normal PDF document processing operations.
Mitigation strategies for CVE-2017-14976 should prioritize immediate software updates to Poppler versions that contain the patched implementation of the FoFiType1C::convertToType0 function. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing Poppler-based PDF processing are updated promptly. Additionally, input validation measures can be implemented at the application level to detect and reject malformed PDF documents before they reach the vulnerable library functions. Security monitoring should include detection of unusual memory access patterns or application crashes that might indicate exploitation attempts. The vulnerability's characteristics align with ATT&CK technique T1203, which covers exploitation of software vulnerabilities, and organizations should consider implementing network-based intrusion detection systems that can identify suspicious PDF processing activities. System administrators should also consider implementing sandboxing mechanisms for PDF processing to limit the potential impact of successful exploitation attempts, particularly in high-risk environments where PDF documents are frequently processed from untrusted sources.