CVE-2016-9533 in macOS
Summary
by MITRE
tif_pixarlog.c in libtiff 4.0.6 has out-of-bounds write vulnerabilities in heap allocated buffers. Reported as MSVR 35094, aka "PixarLog horizontalDifference heap-buffer-overflow."
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Analysis
by VulDB Data Team • 11/20/2022
The vulnerability identified as CVE-2016-9533 represents a critical heap buffer overflow flaw within the libtiff library version 4.0.6 specifically in the tif_pixarlog.c module. This issue manifests as an out-of-bounds write condition that occurs when processing PixarLog format TIFF files, making it particularly dangerous for applications that handle untrusted image data. The vulnerability was originally reported as Microsoft Security Vulnerability Report 35094 and is commonly referred to as "PixarLog horizontalDifference heap-buffer-overflow" due to its specific trigger mechanism within the PixarLog compression handling code.
The technical flaw stems from improper bounds checking during the horizontal difference calculation process within the PixarLog compression algorithm. When the library processes a specially crafted TIFF file containing PixarLog compression, the horizontalDifference function attempts to write data beyond the allocated heap buffer boundaries. This occurs because the code fails to validate the input parameters that determine buffer sizes and write positions, allowing an attacker to control the amount of data written beyond the intended buffer limits. The vulnerability is classified as a heap buffer overflow under CWE-121, which specifically addresses heap-based buffer overflow conditions where insufficient bounds checking permits writes beyond allocated memory regions. This particular implementation flaw demonstrates a classic lack of input validation and memory management oversight that has been documented in numerous security advisories over the years.
The operational impact of this vulnerability extends far beyond simple denial of service scenarios, as it can potentially lead to remote code execution when exploited in applications that process untrusted TIFF files. Systems utilizing libtiff 4.0.6 for image processing, document management, or digital asset handling are at risk, particularly those that accept user-uploaded images or process files from external sources. The vulnerability's exploitation potential aligns with ATT&CK technique T1203, which covers "Exploitation for Client Execution" where adversaries leverage software vulnerabilities to execute malicious code. Applications such as web servers processing image uploads, content management systems, digital photography software, and image processing pipelines become prime targets for exploitation. The heap overflow can result in arbitrary code execution, data corruption, or system crashes, depending on the specific exploitation method and target environment.
Mitigation strategies for CVE-2016-9533 require immediate patching of the libtiff library to version 4.0.7 or later, where the buffer overflow has been corrected through proper bounds checking implementation. System administrators should prioritize updating all applications that depend on libtiff, particularly those handling untrusted image data. Additional defensive measures include implementing strict input validation for TIFF file processing, employing sandboxing techniques for image handling operations, and deploying intrusion detection systems to monitor for potential exploitation attempts. Network segmentation and access controls should be enforced to limit exposure of vulnerable applications to untrusted inputs. The vulnerability serves as a reminder of the critical importance of proper memory management and input validation in security-critical libraries, particularly those handling binary format parsing where malformed inputs can lead to severe memory corruption vulnerabilities. Organizations should also implement regular security assessments of third-party libraries to identify and remediate similar issues before they can be exploited in production environments.