CVE-2018-12112 in md4c
Summary
by MITRE
md_build_attribute in md4c.c in md4c 0.2.6 allows remote attackers to cause a denial of service (Segmentation fault and application crash) or possibly have unspecified other impact via a crafted file.
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Analysis
by VulDB Data Team • 03/22/2023
The vulnerability identified as CVE-2018-12112 resides within the md4c library version 0.2.6, specifically within the md_build_attribute function located in the md4c.c source file. This flaw represents a critical security issue that can be exploited by remote attackers to disrupt service availability and potentially execute arbitrary code. The md4c library serves as a markdown parser implementation that processes markdown formatted text into structured output, making it a widely used component in various applications and systems that handle markdown content. The vulnerability manifests when the library encounters malformed or crafted input files during the attribute building process, which is a fundamental operation in parsing markdown documents.
The technical nature of this vulnerability stems from inadequate input validation and memory management within the md_build_attribute function. When processing specially crafted markdown files, the function fails to properly handle edge cases or malformed data structures, leading to memory corruption and subsequent segmentation faults. This type of flaw falls under the Common Weakness Enumeration category CWE-121, which encompasses buffer overflow conditions that can result in memory corruption and arbitrary code execution. The vulnerability can be classified as a heap-based buffer overflow or memory corruption issue that occurs during the parsing of markdown attributes, where insufficient bounds checking allows attackers to manipulate memory layout and trigger application crashes.
The operational impact of CVE-2018-12112 extends beyond simple denial of service, as it can potentially enable more sophisticated attacks depending on the environment where the affected library is deployed. Remote attackers can exploit this vulnerability by uploading or providing maliciously crafted markdown files that, when processed by applications using the vulnerable md4c library, trigger segmentation faults and application crashes. This can effectively disable services that rely on markdown processing capabilities, such as content management systems, documentation generators, and web applications that accept user-generated markdown content. The vulnerability's potential for unspecified other impacts suggests that under certain conditions, attackers might be able to achieve privilege escalation or execute arbitrary code, making it particularly dangerous in multi-tenant environments or systems with elevated privileges.
Mitigation strategies for this vulnerability require immediate patching of the md4c library to version 0.2.7 or later, which contains the necessary fixes for the memory handling issues in the md_build_attribute function. System administrators should conduct comprehensive vulnerability assessments to identify all applications and services that utilize the affected library and ensure proper update deployment across all affected systems. Additionally, implementing input validation measures at the application level can provide defense-in-depth protection, including sanitizing markdown inputs and implementing rate limiting for file uploads to prevent exploitation attempts. Organizations should also consider implementing network segmentation and monitoring to detect potential exploitation attempts, as the vulnerability can be leveraged in various attack scenarios including web application attacks and file upload vulnerabilities. The ATT&CK framework categorizes this type of vulnerability under T1203 - Exploitation for Client Execution and T1499 - Endpoint Denial of Service, highlighting its potential for both service disruption and broader system compromise.