CVE-2019-9687 in PoDoFo
Summary
by MITRE
PoDoFo 0.9.6 has a heap-based buffer overflow in PdfString::ConvertUTF16toUTF8 in base/PdfString.cpp.
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Analysis
by VulDB Data Team • 07/31/2023
The vulnerability identified as CVE-2019-9687 represents a critical heap-based buffer overflow within the PoDoFo document processing library version 0.9.6. This flaw exists in the PdfString::ConvertUTF16toUTF8 function located in the base/PdfString.cpp source file, making it a significant security concern for any system processing pdf documents. The vulnerability arises from insufficient bounds checking when converting unicode text from utf-16 encoding to utf-8 encoding, creating an exploitable condition that could allow attackers to manipulate memory layout through carefully crafted malicious pdf files.
The technical implementation of this vulnerability stems from improper memory management during string conversion operations. When PoDoFo processes pdf documents containing utf-16 encoded text, the ConvertUTF16toUTF8 function fails to validate the length of input data against allocated buffer boundaries. This oversight creates a scenario where maliciously constructed utf-16 sequences can cause the function to write beyond the intended memory allocation, resulting in heap corruption. The vulnerability falls under the common weakness enumeration CWE-121, which categorizes heap-based buffer overflows as a fundamental memory safety issue. Attackers could potentially leverage this condition to execute arbitrary code or cause application crashes through controlled memory corruption.
The operational impact of CVE-2019-9687 extends beyond simple application instability, as it presents a viable attack vector for remote code execution in environments where pdf processing occurs. Systems utilizing PoDoFo for document handling, including web applications, document management systems, and pdf rendering services, become vulnerable to exploitation. The vulnerability is particularly concerning in server environments where pdf files are processed without proper sanitization, as attackers could craft malicious pdf documents designed to trigger the buffer overflow during normal processing operations. This condition aligns with attack techniques documented in the mitre attack framework under the T1203 category, which involves exploitation of input validation vulnerabilities to achieve code execution.
Mitigation strategies for this vulnerability require immediate patching of the PoDoFo library to version 0.9.7 or later, where the buffer overflow has been addressed through proper bounds checking implementation. Organizations should also implement defensive measures such as pdf file validation and sanitization before processing, particularly in web applications that accept user-uploaded documents. Additional protections include runtime application security monitoring to detect anomalous memory access patterns and network-based intrusion detection systems to identify potential exploitation attempts. The fix implemented by the PoDoFo development team involved strengthening the input validation logic within the PdfString::ConvertUTF16toUTF8 function to ensure that output buffer sizes properly accommodate the converted utf-8 data, thereby preventing the heap corruption that previously occurred. Security teams should also consider implementing application whitelisting policies and restricting pdf processing to trusted sources to minimize exposure risk while patches are deployed.