CVE-2019-19819 in Free PDF Reader
Summary
by MITRE
The JBIG2Globals library in npdf.dll in Nitro Free PDF Reader 12.0.0.112 has a CAPPDAnnotHandlerUtils::PDAnnotHandlerDestroyData2+0x90ec NULL Pointer Dereference via crafted Unicode content.
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Analysis
by VulDB Data Team • 03/20/2024
The vulnerability identified as CVE-2019-19819 represents a critical NULL pointer dereference flaw within the JBIG2Globals library component of Nitro Free PDF Reader version 12.0.0.112. This issue manifests specifically in the npdf.dll module where the CAPPDAnnotHandlerUtils::PDAnnotHandlerDestroyData2 function contains a memory access error at offset 0x90ec that occurs when processing crafted Unicode content. The flaw demonstrates characteristics consistent with a denial of service condition that could potentially be exploited by malicious actors to disrupt the normal operation of the affected software.
The technical nature of this vulnerability stems from improper input validation within the PDF annotation handling mechanism of the Nitro Free PDF Reader. When the application encounters specially crafted Unicode characters within PDF documents, the processing logic fails to properly validate pointer references before attempting to dereference them. This particular NULL pointer dereference occurs during the cleanup phase of annotation handling, specifically within the PDAnnotHandlerDestroyData2 function where the application attempts to free or process memory structures without first confirming that the pointers are valid. The vulnerability is classified under CWE-476 as a NULL Pointer Dereference, which represents a common class of memory safety issues that can lead to application crashes or potentially more severe exploitation scenarios.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it creates opportunities for attackers to disrupt user workflows and potentially gain unauthorized access to system resources. When a user opens a maliciously crafted PDF document containing the specific Unicode sequences, the application will crash or freeze, preventing normal document processing. This behavior aligns with ATT&CK technique T1203, which involves gaining access to systems through application or system exploitation, though the immediate impact appears to be limited to service disruption rather than privilege escalation. The vulnerability affects any system running Nitro Free PDF Reader 12.0.0.112, making it particularly concerning for enterprise environments where PDF processing is common.
Mitigation strategies for this vulnerability should focus on immediate patch application and implementation of additional security controls. Users should upgrade to the latest version of Nitro Free PDF Reader where this vulnerability has been addressed through proper pointer validation and null checking mechanisms. Organizations should also consider implementing PDF content filtering and sandboxing solutions to prevent potentially malicious documents from reaching end users. Network administrators can deploy intrusion detection systems to monitor for exploitation attempts and implement application whitelisting policies to restrict execution of untrusted PDF viewers. The fix typically involves adding null pointer checks before memory operations and ensuring proper error handling during annotation processing. Additionally, security teams should conduct vulnerability assessments to identify other potentially affected versions of the Nitro PDF suite and implement comprehensive monitoring for similar memory safety issues across the organization's software ecosystem.