CVE-2016-6892 in MatrixSSL
Summary
by MITRE
The x509FreeExtensions function in MatrixSSL before 3.8.6 allows remote attackers to cause a denial of service (free of unallocated memory) via a crafted X.509 certificate.
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Analysis
by VulDB Data Team • 11/12/2024
The vulnerability identified as CVE-2016-6892 resides within the MatrixSSL library version 3.8.5 and earlier, specifically within the x509FreeExtensions function. This flaw represents a classic memory management issue that can be exploited to cause a denial of service condition. The vulnerability occurs when processing X.509 certificates that contain crafted extensions, leading to the freeing of memory that was never allocated or has already been freed. Such improper memory handling creates a condition where the application attempts to release memory resources that are either invalid or have already been deallocated, resulting in system instability and potential service disruption. The issue falls under the category of improper handling of memory resources, which is categorized as CWE-415 in the Common Weakness Enumeration framework. This weakness is particularly dangerous because it can be triggered remotely without requiring authentication, making it an attractive target for attackers seeking to disrupt services.
The technical exploitation of this vulnerability involves sending a specially crafted X.509 certificate to a system running an affected version of MatrixSSL. When the certificate processing routine encounters the malformed extensions within the certificate, it invokes the x509FreeExtensions function which then attempts to free memory locations that do not correspond to allocated memory blocks. This can result in memory corruption, application crashes, or complete system hangs. The attack vector is particularly concerning as it operates at the SSL/TLS layer where many critical services rely on secure communication, making the impact far-reaching across various networked applications. The vulnerability demonstrates poor input validation and memory management practices that are commonly associated with buffer overflows and memory corruption issues, which aligns with ATT&CK technique T1499.201 for Denial of Service through resource exhaustion or memory corruption.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of critical network services. Systems utilizing MatrixSSL for secure communications, including web servers, email servers, and VPN services, could experience complete service outages when subjected to this attack. The vulnerability affects the fundamental security infrastructure of many applications, as SSL/TLS libraries are integral to secure communications across the internet. Organizations may find their services temporarily or permanently unavailable, leading to business disruption and potential financial losses. The memory corruption resulting from this flaw can also create conditions where subsequent operations might fail unpredictably, compounding the impact on system stability and reliability. This type of vulnerability is particularly challenging to detect and remediate as it often manifests only under specific conditions involving malformed certificate data, making it difficult to identify during routine security testing or penetration assessments.
Mitigation strategies for CVE-2016-6892 focus primarily on upgrading to MatrixSSL version 3.8.6 or later, where the memory management issue has been resolved through proper input validation and memory handling procedures. Organizations should conduct comprehensive inventory assessments to identify all systems running affected versions of MatrixSSL and prioritize their remediation efforts accordingly. Additionally, implementing certificate validation mechanisms that can detect and reject malformed certificates can provide an additional layer of defense against exploitation attempts. Network administrators should consider deploying intrusion detection systems that can monitor for suspicious certificate processing patterns or unusual memory allocation behaviors. The fix implemented in the patched version addresses the root cause by ensuring that memory deallocation only occurs for properly allocated memory blocks and by adding proper validation checks before memory operations. Security teams should also consider implementing certificate monitoring solutions that can automatically detect and alert on potentially malicious certificate structures that might exploit this or similar vulnerabilities. Regular security assessments and vulnerability scanning should include checks for outdated SSL/TLS implementations to prevent similar issues from remaining undetected in the organization's infrastructure.