CVE-2017-13726 in LibTIFF
Summary
by MITRE
There is a reachable assertion abort in the function TIFFWriteDirectorySec() in LibTIFF 4.0.8, related to tif_dirwrite.c and a SubIFD tag. A crafted input will lead to a remote denial of service attack.
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Analysis
by VulDB Data Team • 12/27/2022
The vulnerability identified as CVE-2017-13726 represents a critical denial of service weakness within the LibTIFF library version 4.0.8, specifically manifesting in the TIFFWriteDirectorySec() function located in the tif_dirwrite.c source file. This flaw occurs when processing SubIFD tags within TIFF image files, creating a scenario where an attacker can craft malicious input that triggers an assertion abort condition. The technical nature of this vulnerability places it squarely within the category of software reliability issues that can be exploited to disrupt service availability, making it particularly dangerous in environments where TIFF file processing is a core function.
The root cause of this vulnerability stems from inadequate input validation and error handling within the SubIFD tag processing logic. When the TIFFWriteDirectorySec() function encounters a malformed or specially crafted SubIFD tag structure, it fails to properly validate the tag's attributes before proceeding with directory writing operations. This assertion failure occurs during the directory security check phase, where the function expects certain conditions to be met but encounters unexpected data structures. The flaw demonstrates poor defensive programming practices and highlights the importance of robust input sanitization in image processing libraries that handle complex file formats with multiple nested structures.
From an operational perspective, this vulnerability presents a significant risk for remote denial of service attacks, as it can be triggered through the simple act of processing a maliciously crafted TIFF file. Attackers can exploit this weakness by preparing TIFF files containing specially constructed SubIFD tags that cause the assertion to fail when the LibTIFF library attempts to write directory structures. The impact extends beyond individual file processing to potentially affect entire applications or systems that rely on LibTIFF for image handling, including web applications, document management systems, and image processing pipelines. This vulnerability particularly affects systems where TIFF files are processed automatically without proper validation or sandboxing mechanisms.
The security implications of CVE-2017-13726 align with CWE-617, which addresses reachable assertions that can be triggered by external input, and demonstrates characteristics consistent with ATT&CK technique T1499.002 for network denial of service attacks. Organizations using affected versions of LibTIFF should prioritize immediate patching to address this vulnerability, as the assertion abort can cause applications to crash or become unresponsive. Recommended mitigations include updating to LibTIFF version 4.0.9 or later, implementing proper input validation at application boundaries, and deploying sandboxing mechanisms for TIFF file processing. Additionally, network-level defenses such as file type filtering and content inspection can provide additional protection against exploitation attempts targeting this specific vulnerability.