CVE-2011-1681 in Open Virtual Machine Tools
Summary
by MITRE
vmware-hgfsmounter in VMware Open Virtual Machine Tools (aka open-vm-tools) 8.4.2-261024 and earlier attempts to append to the /etc/mtab file without first checking whether resource limits would interfere, which allows local users to trigger corruption of this file via a process with a small RLIMIT_FSIZE value, a related issue to CVE-2011-1089.
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Analysis
by VulDB Data Team • 11/02/2021
The vulnerability identified as CVE-2011-1681 affects VMware Open Virtual Machine Tools version 8.4.2-261024 and earlier releases, specifically targeting the vmware-hgfsmounter component. This flaw represents a critical issue in how the virtualization software handles file system mounting operations within virtual machine environments. The vulnerability stems from insufficient resource limit validation during file manipulation operations, creating a potential pathway for local privilege escalation and system instability. The affected component operates as part of the broader open-vm-tools suite that enables enhanced guest operating system integration in VMware virtualized environments, making it a significant concern for virtualization administrators and security professionals managing VMware deployments.
The technical implementation of this vulnerability resides in the improper handling of file system mount operations within the VMware virtual machine tools framework. When the vmware-hgfsmounter process attempts to append entries to the /etc/mtab file, it fails to validate whether the current process resource limits, particularly the RLIMIT_FSIZE parameter, would prevent successful file modification. This parameter controls the maximum size of files that can be created by a process, and when set to a very small value, it can prevent the process from writing to the mtab file entirely or cause partial writes that corrupt the file structure. The flaw is particularly dangerous because it allows an attacker with local access to manipulate their process limits to trigger this condition intentionally, creating a scenario where the system's mount table becomes corrupted and potentially renders the virtual machine unstable or unusable.
The operational impact of this vulnerability extends beyond simple file corruption, as it can severely compromise the stability and reliability of virtual machine environments. When the /etc/mtab file becomes corrupted, it can cause mounting operations to fail, leading to data accessibility issues and potential system crashes. This vulnerability specifically aligns with CWE-128, which addresses "Wrap or Overflow" conditions in resource management, and represents a form of resource exhaustion attack that can be leveraged to create persistent system instability. The related vulnerability CVE-2011-1089 further demonstrates the pattern of resource limit handling issues within VMware's virtualization tools, indicating a broader architectural weakness in how these components manage system resources during file system operations. The attack vector requires only local access to the system, making it particularly concerning for environments where untrusted users might have access to virtual machine guest operating systems.
Mitigation strategies for CVE-2011-1681 should focus on immediate patching of affected VMware Open Virtual Machine Tools installations, with priority given to organizations running VMware virtualized environments. System administrators should ensure that all virtual machine tools are updated to versions that address this specific resource limit handling issue. Additionally, monitoring for unusual file system activity and mount table corruption should be implemented as part of security operations procedures. The vulnerability's classification under the ATT&CK framework would place it within the Privilege Escalation category, specifically targeting the use of system resources to create persistent access conditions. Organizations should also consider implementing process limit controls that prevent local users from setting extremely restrictive resource limits, though this approach may interfere with legitimate system operations. Regular security assessments of virtualization environments should include verification of proper resource limit handling in all virtual machine tools components to prevent similar vulnerabilities from being exploited in the future.