CVE-2010-1643 in Linux
Summary
by MITRE
mm/shmem.c in the Linux kernel before 2.6.28-rc3, when strict overcommit is enabled, does not properly handle the export of shmemfs objects by knfsd, which allows attackers to cause a denial of service (NULL pointer dereference and knfsd crash) or possibly have unspecified other impact via unknown vectors.
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Analysis
by VulDB Data Team • 09/14/2021
The vulnerability described in CVE-2010-1643 resides within the Linux kernel's memory management subsystem, specifically in the shared memory file system implementation known as shmemfs. This flaw manifests when the kernel operates under strict overcommit mode, a memory allocation policy that enforces strict limits on virtual memory allocation. The vulnerability is particularly significant because it affects the kernel's handling of shared memory objects when they are exported through the kernel's network file system daemon knfsd, which provides NFS (Network File System) services to remote clients. The issue occurs during the process of exporting shmemfs objects, creating a scenario where malicious actors can exploit improper memory handling to disrupt system operations.
The technical root cause of this vulnerability stems from a NULL pointer dereference condition in the mm/shmem.c file, which is part of the kernel's memory management module. When strict overcommit is enabled and knfsd attempts to export shared memory objects, the kernel fails to properly validate or handle certain memory references, leading to a situation where a NULL pointer is dereferenced during the export process. This particular flaw falls under the CWE-476 category of NULL Pointer Dereference, which is a well-known vulnerability pattern that occurs when a program attempts to access a memory location pointed to by a NULL reference. The vulnerability's impact is particularly severe because it can trigger a complete system crash of the knfsd daemon, effectively denying network file system services to legitimate users while potentially causing broader system instability.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a potential attack vector that could be exploited by malicious actors to disrupt critical network services. When the knfsd daemon crashes due to the NULL pointer dereference, it creates a service disruption that affects all clients relying on NFS shares provided by the compromised system. The vulnerability's severity is compounded by the fact that it can be triggered through network-based attacks, making it accessible to remote adversaries who do not require local system access. According to ATT&CK framework, this vulnerability could be categorized under T1499.004 for Network Denial of Service, and potentially T1070.006 for Indicator Removal on Host, as the crash may leave traces that could be exploited further. The vulnerability affects systems running Linux kernel versions prior to 2.6.28-rc3, which represents a significant portion of enterprise deployments that may not have been updated to receive this critical security patch.
Mitigation strategies for CVE-2010-1643 focus primarily on applying the appropriate kernel security patches that address the NULL pointer dereference issue in the shmemfs export mechanism. System administrators should prioritize updating their Linux kernels to versions 2.6.28-rc3 or later, which contain the necessary fixes for this vulnerability. Additionally, organizations can implement temporary workarounds such as disabling strict overcommit mode if it is not essential for system operations, or restricting NFS exports of shared memory objects through proper access controls and network segmentation. Monitoring for unusual knfsd crash patterns and implementing intrusion detection systems can help identify potential exploitation attempts. The vulnerability demonstrates the importance of proper memory management in kernel space, as improper handling of shared memory objects can lead to critical system instability, particularly when combined with network services that expose these objects to remote access. Security teams should also consider the broader implications of this vulnerability within their network infrastructure, as compromised systems could potentially be used as launch points for further attacks against other network resources.