CVE-2011-1167 in iOS
Summary
by MITRE
Heap-based buffer overflow in the thunder (aka ThunderScan) decoder in tif_thunder.c in LibTIFF 3.9.4 and earlier allows remote attackers to execute arbitrary code via crafted THUNDER_2BITDELTAS data in a .tiff file that has an unexpected BitsPerSample value.
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Analysis
by VulDB Data Team • 07/22/2018
The vulnerability CVE-2011-1167 represents a critical heap-based buffer overflow in the LibTIFF library's ThunderScan decoder component. This flaw exists within the tif_thunder.c file and affects all versions of LibTIFF up to and including 3.9.4. The vulnerability manifests when processing TIFF files containing crafted THUNDER_2BITDELTAS data where the BitsPerSample value is manipulated to an unexpected state, creating a condition that allows attackers to overwrite adjacent heap memory regions. The flaw stems from insufficient bounds checking during the decoding process of ThunderScan compressed TIFF images, where the decoder fails to properly validate the size of data structures before attempting to copy or process them into allocated heap buffers.
The technical implementation of this vulnerability leverages the inherent design of the ThunderScan compression algorithm within LibTIFF, which uses a delta encoding scheme for 2-bit data. When the BitsPerSample field is set to an unexpected value, the decoder calculates buffer sizes based on incorrect assumptions about the data structure layout. This miscalculation results in a situation where the program attempts to write more data than the allocated buffer can accommodate, leading to heap corruption. The overflow can be exploited to overwrite critical heap metadata, function pointers, or other adjacent memory regions, potentially enabling remote code execution. This vulnerability is classified under CWE-121 as a heap-based buffer overflow and aligns with ATT&CK technique T1203 for Exploitation for Execution.
The operational impact of CVE-2011-1167 extends beyond simple remote code execution, as it can be leveraged in various attack scenarios including web application exploitation, file sharing platforms, and document processing systems. Any application that utilizes LibTIFF for TIFF file processing and does not properly validate input files becomes a potential target. The vulnerability is particularly dangerous in server environments where TIFF files are processed automatically, such as content management systems, document conversion services, or image processing pipelines. Attackers can craft malicious TIFF files that trigger the overflow when opened by vulnerable applications, potentially leading to complete system compromise. The exploitation requires careful crafting of the THUNDER_2BITDELTAS data structure and manipulation of the BitsPerSample field to achieve the desired buffer overflow condition.
Mitigation strategies for this vulnerability require immediate patching of all affected LibTIFF versions to 3.9.5 or later, which contains the necessary fixes for the buffer overflow condition. Organizations should implement input validation measures that verify BitsPerSample values against expected ranges and reject TIFF files with inconsistent or unexpected metadata. Additionally, applications using LibTIFF should employ sandboxing techniques and memory protection mechanisms such as stack canaries, address space layout randomization, and data execution prevention to limit the impact of potential exploitation. System administrators should conduct comprehensive vulnerability assessments to identify all systems that may be processing TIFF files, particularly those that automatically process user-uploaded content. The fix implemented by LibTIFF developers addresses the root cause by adding proper bounds checking and validation of the BitsPerSample field before buffer allocation, preventing the overflow condition from occurring. This vulnerability highlights the importance of proper input validation in image processing libraries and demonstrates how seemingly benign metadata fields can become attack vectors when not properly validated against expected value ranges.