CVE-2013-2124 in LibguestFS
Summary
by MITRE
Double free vulnerability in inspect-fs.c in LibguestFS 1.20.x before 1.20.7, 1.21.x, 1.22.0, and 1.23.0 allows remote attackers to cause a denial of service (crash) via empty guest files.
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Analysis
by VulDB Data Team • 03/22/2022
The vulnerability identified as CVE-2013-2124 represents a critical double free condition within the LibguestFS library, specifically in the inspect-fs.c component that handles filesystem inspection operations for virtual machine guests. This flaw exists in LibguestFS versions 1.20.x prior to 1.20.7, 1.21.x series, 1.22.0, and 1.23.0, creating a significant security risk that can be exploited remotely. The vulnerability manifests when the library processes empty guest files, which can occur during normal operation when inspecting virtual machine disk images that contain no data or have been initialized with empty filesystem structures. The double free condition occurs when the same memory block is freed twice during the processing of these empty files, leading to undefined behavior and potential system instability.
The technical implementation of this vulnerability involves the improper handling of memory allocation and deallocation sequences within the filesystem inspection logic. When LibguestFS encounters an empty guest file during inspection, the inspect-fs.c code path fails to properly manage the memory references, resulting in a scenario where a memory block allocated for processing filesystem metadata gets freed once, then freed again, causing the memory allocator to detect the double free condition. This condition is classified under CWE-415 as an improper free, which is a common vulnerability pattern in memory management where a program attempts to free the same memory block more than once, leading to heap corruption and potential arbitrary code execution or system crashes. The flaw specifically affects the library's ability to handle edge cases in guest file processing, particularly when dealing with empty or zero-length filesystem structures that are valid but uncommon in normal usage scenarios.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged by remote attackers to disrupt services that depend on LibguestFS for virtual machine management and inspection tasks. Systems utilizing LibguestFS for automated VM provisioning, backup operations, or virtualization management platforms become vulnerable to crashes when processing maliciously crafted empty guest files. The vulnerability can be exploited through various attack vectors including automated scanning tools, compromised virtual machine images, or maliciously crafted disk images that contain empty filesystem structures designed to trigger the double free condition. This makes the vulnerability particularly dangerous in cloud computing environments, virtualization platforms, and automated infrastructure management systems where LibguestFS is commonly deployed. The potential for remote code execution exists in some configurations, though the primary impact remains denial of service and system instability.
Mitigation strategies for CVE-2013-2124 should prioritize immediate patching of affected LibguestFS installations to versions 1.20.7, 1.21.x, 1.22.0, or 1.23.0 and later where the double free condition has been resolved. System administrators should implement network segmentation and access controls to limit exposure of systems that process guest files, particularly in cloud environments where virtual machine images may come from untrusted sources. Additional defensive measures include implementing input validation and sanitization for all guest file processing operations, monitoring for unusual memory allocation patterns, and deploying intrusion detection systems that can identify potential exploitation attempts. The vulnerability aligns with ATT&CK technique T1489 which involves affecting availability by degrading system services through resource exhaustion or memory corruption, and represents a classic example of how improper memory management in system libraries can create widespread security implications across virtualization platforms. Organizations should also consider implementing automated vulnerability scanning processes that can detect and remediate affected LibguestFS installations within their infrastructure to prevent exploitation of this and similar memory corruption vulnerabilities.