CVE-2018-5295 in PoDoFo
Summary
by MITRE
In PoDoFo 0.9.5, there is an integer overflow in the PdfXRefStreamParserObject::ParseStream function (base/PdfXRefStreamParserObject.cpp). Remote attackers could leverage this vulnerability to cause a denial-of-service via a crafted pdf file.
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Analysis
by VulDB Data Team • 05/26/2020
The vulnerability identified as CVE-2018-5295 represents a critical integer overflow flaw within the PoDoFo library version 0.9.5, specifically within the PdfXRefStreamParserObject::ParseStream function located in base/PdfXRefStreamParserObject.cpp. This issue manifests when processing malformed pdf files that contain crafted xref stream data, creating a scenario where an attacker can manipulate the parsing logic to trigger arithmetic overflow conditions. The integer overflow occurs during the calculation of memory allocation sizes or array indices, where the multiplication or addition of two integers exceeds the maximum representable value for the target data type, resulting in a wraparound behavior that can lead to unpredictable program execution states.
The technical exploitation of this vulnerability requires an attacker to construct a malicious pdf document containing specially crafted xref stream entries that, when processed by the vulnerable PoDoFo library, will cause the integer overflow to occur during stream parsing operations. This parsing function is responsible for interpreting cross-reference streams that are part of the pdf file structure, which contain information about object locations within the file. When the overflow occurs, it typically results in memory corruption or invalid memory access patterns that cause the application using PoDoFo to crash or become unresponsive. The vulnerability is classified as a remote code execution risk in certain contexts, though the primary impact documented is denial-of-service, as the overflow conditions prevent normal processing of valid pdf files.
From an operational perspective, this vulnerability poses significant risks to any system or application that relies on PoDoFo for pdf processing, including web applications, document management systems, email servers, and pdf viewers. The denial-of-service impact can be particularly damaging in environments where pdf processing is critical to business operations, as it can effectively disable pdf handling capabilities for extended periods. The vulnerability is particularly concerning because it can be triggered through simple file uploads or processing of standard pdf documents without requiring any special privileges or complex attack vectors. Systems that process untrusted pdf content from external sources are most vulnerable, as they provide the perfect attack surface for remote exploitation.
The mitigation strategies for CVE-2018-5295 primarily involve upgrading to a patched version of the PoDoFo library where the integer overflow has been addressed through proper input validation and overflow checking mechanisms. Organizations should also implement input sanitization measures that validate pdf file structures before processing, particularly focusing on xref stream data integrity checks. Additionally, deploying sandboxing techniques for pdf processing and implementing strict resource limits can help contain potential impacts if exploitation occurs. This vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and relates to ATT&CK technique T1203, which involves exploiting software vulnerabilities through crafted input files. The remediation process should include comprehensive testing of pdf processing workflows to ensure that the patched library handles all edge cases properly and that no similar vulnerabilities exist in related parsing functions within the codebase.