CVE-2016-9969 in libwebp
Summary
by MITRE
In libwebp 0.5.1, there is a double free bug in libwebpmux.
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Analysis
by VulDB Data Team • 05/23/2025
The vulnerability identified as CVE-2016-9969 represents a critical double free error within the libwebp 0.5.1 library, specifically within the libwebpmux component responsible for handling webp image format manipulation. This flaw occurs when the library processes malformed webp files that contain specially crafted data structures designed to trigger memory management inconsistencies during the decompression and processing phases. The double free vulnerability arises from improper handling of memory allocation and deallocation sequences where the same memory block gets freed twice, potentially leading to memory corruption and arbitrary code execution.
This vulnerability falls under the CWE-415 category of double free conditions, which is classified as a memory safety issue in software development practices. The flaw exists in the memory management routines of libwebpmux where the library fails to properly track memory allocation states when processing certain edge cases in webp file structures. When an attacker crafts a malicious webp file with malformed metadata or corrupted image data, the library's parsing logic can cause it to attempt freeing the same memory location multiple times, creating a condition where the heap management structures become corrupted.
The operational impact of this vulnerability extends across numerous applications and systems that rely on libwebp for image processing, including web browsers, image viewers, content management systems, and mobile applications. Attackers can exploit this vulnerability by delivering malicious webp files through various attack vectors such as web pages, email attachments, or file sharing platforms. The exploitation process typically involves crafting a webp file that triggers the double free condition during image parsing, potentially allowing remote code execution with the privileges of the affected application. This makes the vulnerability particularly dangerous in web browser contexts where users might unknowingly encounter malicious content.
Mitigation strategies for CVE-2016-9969 involve immediate patching of affected systems with updated versions of libwebp that contain proper memory management fixes. Organizations should also implement defensive measures such as input validation for webp file processing, sandboxing of image handling components, and network-level filtering of suspicious file types. Security researchers and system administrators should monitor for exploitation attempts through network traffic analysis and application logs, while also ensuring that all applications using libwebp are regularly updated to prevent exploitation of this and similar memory corruption vulnerabilities. The ATT&CK framework categorizes this vulnerability under the T1059.007 technique for command and scripting interpreter, as exploitation may involve code execution through memory corruption attacks that leverage the double free condition to gain unauthorized system access.