CVE-2012-2745 in Linux
Summary
by MITRE
The copy_creds function in kernel/cred.c in the Linux kernel before 3.3.2 provides an invalid replacement session keyring to a child process, which allows local users to cause a denial of service (panic) via a crafted application that uses the fork system call.
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Analysis
by VulDB Data Team • 03/26/2021
The vulnerability described in CVE-2012-2745 represents a critical flaw in the Linux kernel's credential handling mechanism that affects versions prior to 3.3.2. This issue resides within the copy_creds function located in kernel/cred.c, which is responsible for copying credential information when processes are created through system calls like fork. The flaw specifically manifests when the kernel attempts to provide an invalid replacement session keyring to child processes during the fork operation, creating a scenario where the kernel's security model becomes compromised. The vulnerability demonstrates a fundamental failure in kernel space credential management that can be exploited by local attackers to trigger system-wide instability.
The technical implementation of this vulnerability involves the improper handling of session keyrings during process creation. When a process forks, the kernel must duplicate the parent's credentials including session keyrings that provide access to cryptographic keys and other security tokens. The copy_creds function fails to properly validate or initialize the session keyring for the newly created child process, resulting in a malformed keyring structure that can cause kernel memory corruption. This flaw is particularly dangerous because it occurs during the most fundamental process creation operations, making it accessible through standard system calls without requiring special privileges or complex exploitation techniques. The vulnerability operates at the kernel level and leverages the inherent trust placed in legitimate system operations to create a condition that results in kernel panic.
The operational impact of CVE-2012-2745 extends beyond simple denial of service to represent a serious threat to system stability and availability. Local attackers can exploit this vulnerability by crafting a malicious application that performs fork operations, causing the kernel to panic and potentially leading to complete system crashes or reboots. This vulnerability affects systems running Linux kernel versions before 3.3.2, making it particularly relevant for organizations maintaining older kernel versions or those that have not properly updated their systems. The exploitability is high since it requires only basic local user privileges and standard system calls, making it a preferred target for attackers seeking to disrupt system operations. The vulnerability can be classified under CWE-248 as an Uncaught Exception, where the kernel fails to properly handle an exceptional condition during credential copying.
This vulnerability aligns with several ATT&CK techniques including privilege escalation and denial of service operations. The attack pattern follows the T1068 technique for privilege escalation by exploiting kernel-level flaws to gain control over system resources, while the T1499 technique for network disruption can be achieved through the resulting system instability. The attack surface is broad since any application that uses fork system calls can potentially trigger the vulnerability, making it particularly dangerous in multi-user environments where malicious users can exploit this to disrupt services. Organizations should consider implementing kernel hardening measures and maintaining up-to-date security patches as part of their defensive strategies, as this vulnerability represents a clear indication of inadequate kernel security controls.
The remediation strategy for CVE-2012-2745 requires immediate kernel version updates to 3.3.2 or later, where the vulnerability has been properly addressed through enhanced credential validation and session keyring handling. System administrators should prioritize patching operations and conduct thorough testing to ensure that kernel updates do not introduce compatibility issues with existing applications. The fix implemented in the patched kernel versions addresses the root cause by properly validating session keyring structures during credential copying operations, preventing the creation of malformed keyring objects that could trigger kernel panics. Organizations should also implement monitoring solutions to detect potential exploitation attempts and maintain comprehensive incident response procedures to address any system disruptions that may occur during the patching process.