CVE-2017-9239 in Exiv2
Summary
by MITRE
An issue was discovered in Exiv2 0.26. When the data structure of the structure ifd is incorrect, the program assigns pValue_ to 0x0, and the value of pValue() is 0x0. TiffImageEntry::doWriteImage will use the value of pValue() to cause a segmentation fault. To exploit this vulnerability, someone must open a crafted tiff file.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-9239 represents a critical memory corruption issue within the Exiv2 image processing library version 0.26. This flaw manifests when the Image File Directory (IFD) data structure contains malformed or incorrect information, creating a dangerous condition where the program assigns a null pointer value to pValue_ member variable. The underlying issue stems from insufficient input validation and error handling within the TIFF image parsing routines, specifically affecting how the library processes malformed IFD entries during image metadata extraction. The vulnerability is categorized under CWE-125, which describes out-of-bounds read conditions, and more specifically aligns with CWE-476, null pointer dereference, as the program attempts to access memory through a null reference.
The technical exploitation of this vulnerability occurs through a carefully crafted TIFF file that contains malformed IFD structures designed to trigger the specific code path where pValue_ is set to zero. When the TiffImageEntry::doWriteImage function attempts to process this corrupted data structure, it calls the pValue() method which returns the null pointer value, leading to an immediate segmentation fault or crash. This memory access violation represents a classic null pointer dereference scenario that can be exploited by attackers to cause application termination or potentially achieve more sophisticated attack vectors through controlled memory corruption. The vulnerability exists in the TIFF image processing pipeline and specifically affects the library's ability to safely handle malformed image files without proper bounds checking and validation.
The operational impact of CVE-2017-9239 extends beyond simple application crashes, as it can be leveraged in broader attack scenarios within systems that rely on Exiv2 for image metadata processing. Any application or service that uses Exiv2 to handle user-provided TIFF images, including web applications, content management systems, digital asset management platforms, and image processing utilities, becomes vulnerable to this flaw. The vulnerability can be exploited through file-based attacks where an attacker uploads or sends a maliciously crafted TIFF file, triggering the segmentation fault during image processing. This represents a significant concern for security-conscious organizations that process untrusted image content, as the vulnerability can be used to deny service or potentially escalate privileges depending on the execution context of the vulnerable application.
Mitigation strategies for CVE-2017-9239 should prioritize immediate software updates to Exiv2 version 0.27 or later, where the vulnerability has been addressed through improved input validation and null pointer checks. System administrators should implement strict file validation policies that reject or sanitize TIFF files before processing, particularly when these files originate from untrusted sources. Network-level defenses can include content inspection systems that identify and block suspicious TIFF file patterns, while application-level protections should incorporate proper error handling and memory safety practices. The vulnerability's exploitation pathway aligns with ATT&CK technique T1203, legitimate program execution, as it leverages the normal operation of image processing software to execute malicious code through crafted input. Organizations should also consider implementing sandboxing mechanisms for image processing operations and monitoring for abnormal application behavior that could indicate exploitation attempts.