CVE-2013-4205 in Linux
Summary
by MITRE
Memory leak in the unshare_userns function in kernel/user_namespace.c in the Linux kernel before 3.10.6 allows local users to cause a denial of service (memory consumption) via an invalid CLONE_NEWUSER unshare call.
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Analysis
by VulDB Data Team • 05/21/2021
The vulnerability identified as CVE-2013-4205 represents a critical memory management flaw within the Linux kernel's user namespace implementation. This issue resides in the unshare_userns function located in kernel/user_namespace.c, specifically affecting Linux kernel versions prior to 3.10.6. The vulnerability manifests when local users execute invalid CLONE_NEWUSER unshare system calls, creating a condition where memory allocated for user namespace structures is not properly released back to the system. This memory leak occurs because the kernel fails to validate the legitimacy of the unshare operation before proceeding with memory allocation, allowing malicious or malformed operations to consume system resources without proper cleanup.
The technical exploitation of this vulnerability leverages the kernel's insufficient input validation mechanisms during user namespace manipulation operations. When a process attempts to unshare user namespaces using the CLONE_NEWUSER flag with invalid parameters, the kernel allocates memory for the new user namespace structure but does not properly handle error conditions or cleanup operations. This results in allocated memory pages remaining in use indefinitely, causing progressive memory consumption that can eventually exhaust available system resources. The flaw operates at the kernel level where user namespace management is handled, making it particularly dangerous as it can be triggered by any local user with sufficient privileges to execute system calls, without requiring elevated permissions beyond basic user access.
The operational impact of this memory leak vulnerability extends beyond simple resource exhaustion, creating potential system instability and service disruption. Local users can exploit this vulnerability to gradually consume all available memory on a system, leading to denial of service conditions where legitimate processes cannot allocate necessary memory resources. This type of attack is particularly concerning in multi-user environments where one compromised or malicious user can degrade system performance for all users. The vulnerability affects systems running Linux kernel versions 3.10.5 and earlier, representing a significant security gap that could be exploited in various attack scenarios including resource exhaustion attacks, system degradation, and potential escalation of privileges through memory manipulation techniques.
This vulnerability aligns with CWE-401, which addresses improper handling of memory allocation failures in software systems, and demonstrates characteristics consistent with ATT&CK technique T1499.001 for resource hijacking through memory exhaustion attacks. The flaw represents a classic case of insufficient resource management where the kernel fails to properly implement cleanup routines for failed system calls. Mitigation strategies should focus on upgrading to kernel versions 3.10.6 or later where the vulnerability has been patched, implementing proper input validation mechanisms, and monitoring system memory usage for unusual consumption patterns. Additionally, system administrators should consider implementing process limits and memory quotas to prevent single processes from consuming excessive resources, while regular kernel updates and security audits remain essential for maintaining system integrity against similar memory management vulnerabilities.