CVE-2016-9448 in LibTIFF
Summary
by MITRE
The TIFFFetchNormalTag function in LibTiff 4.0.6 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) by setting the tags TIFF_SETGET_C16ASCII or TIFF_SETGET_C32_ASCII to values that access 0-byte arrays. NOTE: this vulnerability exists because of an incomplete fix for CVE-2016-9297.
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Analysis
by VulDB Data Team • 05/15/2026
The vulnerability identified as CVE-2016-9448 represents a critical denial of service flaw within the LibTiff library version 4.0.6, specifically affecting the TIFFFetchNormalTag function. This issue demonstrates how security patches can sometimes introduce new vulnerabilities when they are incomplete or fail to address all potential attack vectors. The flaw manifests when processing TIFF image files that contain specially crafted tags with the identifiers TIFF_SETGET_C16ASCII or TIFF_SETGET_C32_ASCII, which are designed for handling 16-bit and 32-bit ASCII data respectively. The vulnerability arises from improper validation of array boundaries when these specific tag types are processed, creating a scenario where a NULL pointer dereference occurs during normal file parsing operations.
The technical implementation of this vulnerability stems from a flawed handling of memory access patterns within the TIFF file parsing logic. When the TIFFFetchNormalTag function encounters these specific tag types with zero-length array values, the underlying code fails to properly validate the array bounds before attempting to access memory locations. This results in a NULL pointer dereference that crashes the application process and leads to a complete denial of service condition. The vulnerability is particularly concerning because it can be triggered remotely through the processing of maliciously crafted TIFF files, making it an attractive target for attackers seeking to disrupt services that rely on LibTiff for image processing. The flaw is classified under CWE-476 as a NULL pointer dereference, which represents a fundamental memory safety issue that can lead to application instability and system compromise.
From an operational perspective, this vulnerability poses significant risks to systems that process TIFF image files from untrusted sources, including web applications, image processing servers, and document management systems. Attackers can exploit this weakness by uploading or transmitting specially crafted TIFF files that trigger the NULL pointer dereference during parsing, causing the affected application to crash and potentially leading to service interruption. The vulnerability's remote exploitability means that systems processing user-uploaded content or receiving TIFF files from external sources are particularly at risk. The fact that this vulnerability emerged from an incomplete fix for CVE-2016-9297 highlights the complexity of security patching and the importance of thorough regression testing when addressing security issues in widely-used libraries. Organizations using LibTiff 4.0.6 or earlier versions should prioritize immediate patching to mitigate this risk.
The remediation approach for CVE-2016-9448 requires updating to a patched version of LibTiff that properly addresses the NULL pointer dereference issue in the TIFFFetchNormalTag function. Security researchers should implement comprehensive input validation for all tag types, particularly those handling variable-length arrays, to prevent access to invalid memory locations. The fix should include proper boundary checking before array access operations and ensure that zero-length arrays are handled gracefully without causing application crashes. Additionally, system administrators should consider implementing proper input sanitization at the application level and monitoring for unusual crash patterns that might indicate exploitation attempts. This vulnerability serves as a reminder of the importance of maintaining up-to-date security patches and the potential for regressions in security fixes, aligning with ATT&CK technique T1211 for privilege escalation through application vulnerabilities and T1499 for network denial of service attacks targeting specific software components. Organizations should also implement automated vulnerability scanning to detect potentially affected systems and ensure that all third-party libraries are regularly updated to address known security issues.