CVE-2016-3634 in LibTIFF
Summary
by MITRE
The tagCompare function in tif_dirinfo.c in the thumbnail tool in LibTIFF 4.0.6 and earlier allows remote attackers to cause a denial of service (out-of-bounds read) via vectors related to field_tag matching.
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Analysis
by VulDB Data Team • 04/30/2019
The vulnerability identified as CVE-2016-3634 represents a critical out-of-bounds read flaw within the LibTIFF library's thumbnail processing functionality. This issue resides in the tagCompare function located within the tif_dirinfo.c file, which is part of the thumbnail tool component of LibTIFF version 4.0.6 and earlier. The vulnerability manifests when the library processes TIFF files containing malformed or specially crafted thumbnail data, creating a scenario where an attacker can manipulate field_tag matching operations to trigger memory access violations. The root cause stems from insufficient input validation and boundary checking within the tag comparison logic, which fails to properly validate the range of tag values during thumbnail processing operations.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a malicious TIFF file with malformed thumbnail data that causes the tagCompare function to access memory locations beyond the allocated buffer boundaries. This out-of-bounds read vulnerability can be triggered during normal TIFF file parsing operations, particularly when the library attempts to match field tags against expected values. The flaw does not directly enable code execution but instead results in a denial of service condition where the application crashes or becomes unresponsive due to invalid memory access patterns. The vulnerability aligns with CWE-125, which specifically addresses out-of-bounds read conditions, and can be categorized under the ATT&CK technique T1499.004 for Network Denial of Service. The impact is particularly severe in environments where LibTIFF is used to process untrusted TIFF files from external sources, such as web applications, email systems, or document processing pipelines.
The operational impact of CVE-2016-3634 extends beyond simple service disruption to potentially compromise entire document processing workflows and application availability. Systems utilizing LibTIFF for image processing, particularly those handling user-uploaded content or external data sources, become vulnerable to denial of service attacks that can render applications unavailable to legitimate users. The vulnerability affects any software that depends on LibTIFF 4.0.6 or earlier versions for thumbnail generation or TIFF file processing, including web servers, document management systems, image processing applications, and various content management platforms. Attackers can exploit this vulnerability by simply providing a maliciously crafted TIFF file that triggers the out-of-bounds read condition during thumbnail parsing, making the attack vector extremely accessible and potentially automated. Organizations relying on vulnerable versions of LibTIFF should consider this vulnerability as a critical security risk requiring immediate remediation to prevent potential service disruption attacks.
Mitigation strategies for CVE-2016-3634 primarily focus on upgrading to patched versions of LibTIFF where the vulnerability has been addressed through proper boundary checking and input validation. The recommended approach involves updating to LibTIFF version 4.0.7 or later, which includes fixes for the tagCompare function that prevent out-of-bounds memory access during field_tag matching operations. System administrators should also implement input validation measures that filter or reject suspicious TIFF files before processing, particularly those with unusual thumbnail structures or malformed metadata. Additional protective measures include deploying network segmentation to limit exposure of vulnerable applications, implementing application firewalls to monitor for suspicious TIFF file processing patterns, and establishing regular vulnerability scanning procedures to identify systems running outdated LibTIFF versions. Organizations should also consider implementing sandboxing techniques for TIFF file processing to contain potential impacts of similar vulnerabilities and maintain detailed logging of file processing activities to detect exploitation attempts. The fix implemented in newer versions typically involves adding proper bounds checking to ensure that tag values remain within expected ranges during comparison operations, thereby preventing the out-of-bounds memory access that leads to the denial of service condition.