CVE-2016-9011 in libwmf
Summary
by MITRE
The wmf_malloc function in api.c in libwmf 0.2.8.4 allows remote attackers to cause a denial of service (application crash) via a crafted wmf file, which triggers a memory allocation failure.
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Analysis
by VulDB Data Team • 09/12/2020
The vulnerability identified as CVE-2016-9011 resides within the libwmf library version 0.2.8.4, specifically in the wmf_malloc function located in the api.c file. This flaw represents a classic denial of service vulnerability that can be exploited by remote attackers through the careful crafting of malicious WMF (Windows Metafile) files. The libwmf library serves as a converter for WMF graphics files, enabling applications to process and render these vector graphics formats across different platforms. When a vulnerable application processes a specially crafted WMF file, the memory allocation mechanism fails catastrophically, leading to application instability and potential crashes that can be leveraged for service disruption.
The technical root cause of this vulnerability stems from inadequate input validation and memory management within the wmf_malloc function. When processing malformed WMF data, the function fails to properly handle edge cases during memory allocation operations, resulting in a scenario where memory allocation requests cannot be fulfilled correctly. This memory allocation failure manifests as an application crash, effectively causing a denial of service condition that prevents legitimate users from accessing the affected service or application. The vulnerability operates at the memory management layer, making it particularly dangerous as it can be triggered simply by opening or processing a malicious file without any additional user interaction beyond the initial file handling.
From an operational impact perspective, this vulnerability presents a significant risk to systems that rely on libwmf for graphic processing, including web servers, document processing applications, and any software that handles WMF file formats. The remote exploitation capability means that attackers can potentially compromise services without requiring local access or user interaction beyond delivering the malicious file. This makes the vulnerability particularly attractive for automated attacks and can be easily incorporated into larger attack frameworks targeting web applications that process user-uploaded graphics. The vulnerability aligns with CWE-122, which addresses improper restriction of operations within a memory buffer, and can be categorized under ATT&CK technique T1499.1, which involves network denial of service attacks through resource exhaustion or manipulation.
The exploitation of this vulnerability requires minimal technical expertise, as it can be executed through standard file delivery methods such as email attachments, web downloads, or file upload mechanisms. Security professionals should consider this vulnerability as part of broader vulnerability management strategies, particularly in environments where legacy graphics processing capabilities are maintained. Organizations using libwmf in their infrastructure should prioritize patching efforts, as the vulnerability provides a straightforward path to service disruption that can be easily automated. The remediation approach typically involves updating to a patched version of libwmf or implementing strict input validation and sanitization measures for all WMF file processing. Additionally, network segmentation and application whitelisting can provide additional defensive layers against potential exploitation attempts, though these measures are secondary to the primary requirement of updating the vulnerable library components.