CVE-2012-2652 in Qemu
Summary
by MITRE
The bdrv_open function in Qemu 1.0 does not properly handle the failure of the mkstemp function, when in snapshot node, which allows local users to overwrite or read arbitrary files via a symlink attack on an unspecified temporary file.
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Analysis
by VulDB Data Team • 12/07/2021
The vulnerability identified as CVE-2012-2652 resides within the Qemu virtualization software version 1.0, specifically within the bdrv_open function that manages block device operations. This flaw represents a critical security issue that stems from inadequate error handling mechanisms when the mkstemp function fails during snapshot node operations. The mkstemp function is designed to create temporary files securely by generating unique filenames and ensuring proper file permissions, but the vulnerability occurs when this function encounters failure conditions that are not properly accounted for in the Qemu codebase. When the mkstemp function fails, the system should ideally abort the operation or handle the error gracefully, but instead the code continues execution without proper safeguards, creating a dangerous scenario for file system operations.
The technical exploitation of this vulnerability involves a symlink attack that targets an unspecified temporary file created during snapshot node processing. Attackers can manipulate the file system by creating symbolic links that point to sensitive target files, then trigger the vulnerable code path through legitimate Qemu operations. When the bdrv_open function processes these snapshot operations, it attempts to create temporary files but fails to properly validate or handle the mkstemp failure, allowing malicious users to influence which files are actually accessed or modified. This creates a privilege escalation scenario where local users can potentially overwrite critical system files or read sensitive data that they would normally not have access to, fundamentally undermining the security boundaries that virtualization software should maintain.
The operational impact of this vulnerability extends beyond simple file system manipulation as it represents a fundamental failure in secure temporary file handling practices that affects the entire Qemu virtualization ecosystem. Virtual machine administrators and users who rely on Qemu for their computing environments face significant risks when this vulnerability exists, as it allows attackers to bypass normal file access controls and potentially escalate privileges to gain unauthorized access to system resources. The vulnerability affects not only the immediate file system operations but also the broader security model of virtualization platforms where Qemu serves as a core component, potentially enabling attackers to compromise guest operating systems or even host systems depending on the specific implementation and access controls in place.
This vulnerability aligns with several established security frameworks and threat models, particularly CWE-367 which addresses the Time-of-Check to Time-of-Use (TOCTOU) race condition, and CWE-22 which covers improper limitation of a pathname to a restricted directory. The attack vector described in the CVE follows patterns consistent with ATT&CK technique T1059 which involves executing malicious code through command-line interfaces, and T1068 which covers privilege escalation through local exploitation. The security implications extend to the broader concept of secure file handling practices as outlined in the OWASP Secure Coding Practices, where proper error handling and temporary file management are critical components of secure software development. Organizations using Qemu 1.0 or similar virtualization platforms should implement immediate mitigations including upgrading to patched versions, implementing proper file system access controls, and monitoring for suspicious file system activities that could indicate exploitation attempts.
The remediation approach for this vulnerability requires both immediate and long-term security measures to address the root cause of the inadequate error handling. Immediate fixes should involve upgrading to Qemu versions that properly handle mkstemp function failures and implement robust error checking mechanisms. System administrators should also consider implementing additional security controls such as restricted file system permissions, mandatory access controls, and enhanced monitoring of temporary file creation and usage patterns. The vulnerability highlights the importance of following secure coding practices specifically around temporary file handling and error management, where the failure to properly handle system calls can create exploitable conditions that fundamentally compromise system security. Regular security audits and code reviews focusing on error handling patterns, particularly around file system operations and temporary file management, should be implemented to prevent similar issues from occurring in other software components within the virtualization stack.