CVE-2019-19817 in Free PDF Reader
Summary
by MITRE
The JBIG2Decode library in npdf.dll in Nitro Free PDF Reader 12.0.0.112 has a CAPPDAnnotHandlerUtils::PDAnnotHandlerDestroyData2+0x2e8a Out-of-Bounds Read via crafted Unicode content.
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Analysis
by VulDB Data Team • 03/20/2024
The vulnerability CVE-2019-19817 represents a critical out-of-bounds read condition within the JBIG2Decode library component of Nitro Free PDF Reader version 12.0.0.112. This flaw exists in the npdf.dll module and specifically manifests in the CAPPDAnnotHandlerUtils::PDAnnotHandlerDestroyData2 function at offset 0x2e8a. The vulnerability is triggered when processing crafted Unicode content within PDF annotations, making it particularly dangerous in environments where users may encounter untrusted PDF documents. The issue stems from inadequate input validation and memory management practices within the PDF annotation handling subsystem.
This vulnerability falls under the CWE-125 Out-of-Bounds Read classification and represents a memory safety issue that can lead to arbitrary code execution or system instability. The flaw occurs during the destruction phase of PDF annotation data processing where the application fails to properly validate the bounds of Unicode character sequences before accessing memory locations. The specific offset 0x2e8a indicates a precise location within the function where the out-of-bounds access occurs, suggesting a well-defined buffer overrun condition that could be exploited by an attacker. The attack vector requires the victim to open a malicious PDF document containing specially crafted Unicode content that triggers the vulnerable code path.
The operational impact of this vulnerability is significant as it can be leveraged for remote code execution when users open malicious PDF files. Attackers can craft PDF documents with malformed Unicode sequences that, when processed by the vulnerable Nitro Free PDF Reader, cause the application to read memory beyond allocated bounds. This could result in information disclosure, application crashes, or potentially full system compromise depending on the execution environment. The vulnerability affects the broader PDF processing ecosystem and demonstrates the risks associated with complex multimedia decoding libraries that handle various encoding formats including JBIG2 compression standards. Security researchers have noted that this type of vulnerability often indicates deeper architectural issues in memory management and input validation.
Mitigation strategies for CVE-2019-19817 should include immediate patching of the Nitro Free PDF Reader to version 12.0.0.113 or later, which contains the necessary memory bounds checking and input validation fixes. Organizations should implement strict PDF document scanning and validation procedures before allowing user access to potentially malicious content. The ATT&CK framework categorizes this vulnerability under T1203 Exploitation for Client Execution and T1059 Command and Scripting Interpreter, highlighting the need for defensive measures such as application whitelisting, sandboxing PDF processing, and network-based intrusion detection systems. Additionally, users should be educated about the risks of opening untrusted PDF documents and organizations should consider implementing email filtering and web proxy solutions that can detect and block malicious PDF content before it reaches end users.