CVE-2017-5852 in PoDoFo
Summary
by MITRE
The PoDoFo::PdfPage::GetInheritedKeyFromObject function in base/PdfVariant.cpp in PoDoFo 0.9.4 allows remote attackers to cause a denial of service (infinite loop) via a crafted file.
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Analysis
by VulDB Data Team • 10/15/2019
The vulnerability identified as CVE-2017-5852 represents a critical denial of service flaw within the PoDoFo library version 0.9.4, specifically affecting the PdfPage::GetInheritedKeyFromObject function located in base/PdfVariant.cpp. This issue arises from improper handling of PDF object inheritance mechanisms during document parsing, creating a condition where maliciously crafted PDF files can trigger an infinite loop in the library's processing logic. The flaw demonstrates a classic example of inadequate input validation and recursive processing control, where the library fails to properly terminate inheritance resolution when encountering circular references or malformed object structures.
The technical implementation of this vulnerability stems from the function's inability to detect and break infinite recursion patterns when traversing PDF object inheritance chains. When processing a specially crafted PDF document, the GetInheritedKeyFromObject function enters a loop where it repeatedly references parent objects without proper cycle detection mechanisms. This behavior aligns with CWE-838, which categorizes improper handling of input that can lead to resource exhaustion, and specifically relates to CWE-400 which addresses unchecked resource consumption through infinite loops. The function processes PDF objects by following inheritance paths from child to parent objects, but lacks proper safeguards to identify when the same object has been visited multiple times during the traversal process.
From an operational perspective, this vulnerability presents a significant risk to any system or application that relies on PoDoFo for PDF processing, including document management systems, web applications, and content filtering solutions. Attackers can exploit this flaw by crafting malicious PDF files that contain circular inheritance references, causing the target system to consume excessive CPU resources and potentially leading to system unresponsiveness or complete service denial. The impact extends beyond simple resource exhaustion as it can affect multiple concurrent users if the vulnerability is present in shared processing environments. This type of vulnerability is particularly dangerous in server environments where PDF processing is a common operation, as it can be leveraged for DoS attacks against critical infrastructure.
The exploitation of this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks through resource exhaustion. Organizations using PoDoFo libraries should prioritize immediate remediation through version updates to 0.9.5 or later, as this vulnerability was specifically addressed in subsequent releases. Mitigation strategies include implementing proper input validation at the application level, establishing timeout mechanisms for PDF processing operations, and deploying sandboxing techniques to isolate PDF handling components. Additionally, network-based intrusion detection systems should be configured to monitor for suspicious PDF file patterns that might indicate exploitation attempts, while regular security assessments should verify that all PDF processing components are updated to versions free from known vulnerabilities. The fix implemented in newer versions typically involves adding cycle detection algorithms and proper recursion depth limiting to prevent the infinite loop condition from occurring during object inheritance resolution.