CVE-2011-4077 in Linux
Summary
by MITRE
Buffer overflow in the xfs_readlink function in fs/xfs/xfs_vnodeops.c in XFS in the Linux kernel 2.6, when CONFIG_XFS_DEBUG is disabled, allows local users to cause a denial of service (memory corruption and crash) and possibly execute arbitrary code via an XFS image containing a symbolic link with a long pathname.
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Analysis
by VulDB Data Team • 03/19/2021
The vulnerability identified as CVE-2011-4077 represents a critical buffer overflow flaw within the XFS file system implementation of the Linux kernel version 2.6. This issue specifically affects the xfs_readlink function located in fs/xfs/xfs_vnodeops.c and demonstrates how improper input validation can lead to severe system instability and potential privilege escalation. The vulnerability manifests when the CONFIG_XFS_DEBUG kernel configuration option is disabled, which is the default setting in most production environments, making the flaw particularly dangerous as it affects standard kernel deployments.
The technical root cause of this vulnerability stems from inadequate bounds checking within the xfs_readlink function, which processes symbolic links in XFS file systems. When a maliciously crafted XFS image contains a symbolic link with an excessively long pathname, the function fails to properly validate the length of the target path before attempting to copy it into a fixed-size buffer. This buffer overflow condition occurs because the implementation does not account for the possibility of extremely long symbolic link targets, leading to memory corruption that can overwrite adjacent memory locations. The vulnerability operates at the kernel level, where buffer overflows can result in unpredictable behavior including system crashes, memory corruption, and potentially arbitrary code execution.
The operational impact of CVE-2011-4077 extends beyond simple denial of service, as local attackers with the ability to create or modify XFS images can exploit this flaw to compromise system stability. In a typical attack scenario, an adversary would create an XFS image containing a symbolic link with a path exceeding the allocated buffer size, then mount this image on a system running the vulnerable kernel. The system would crash during the readlink operation when processing the malformed symbolic link, causing a kernel panic and complete system outage. However, the vulnerability's potential for code execution arises from the fact that memory corruption can be manipulated to overwrite kernel function pointers or other critical data structures, potentially allowing privilege escalation to kernel level access.
From a cybersecurity perspective, this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and demonstrates how kernel-level buffer overflows can be leveraged for system compromise. The attack vector falls under the ATT&CK framework's privilege escalation techniques, specifically targeting kernel exploits that can be used to gain system-level control. The vulnerability also relates to the broader category of software defects that can be exploited through file system manipulation, as outlined in various cybersecurity frameworks that emphasize the importance of input validation in kernel space operations. Organizations affected by this vulnerability should prioritize kernel updates and consider implementing additional security controls to prevent local users from creating malicious XFS images, as the exploit requires only local access to the system to be effective.
Mitigation strategies for CVE-2011-4077 should focus on immediate kernel patching, as the primary fix involves correcting the buffer size validation within the xfs_readlink function to properly handle long symbolic link paths. System administrators should also implement monitoring for suspicious XFS image creation activities and consider disabling unnecessary XFS debugging features that could expose additional attack surfaces. The vulnerability serves as a reminder of the critical importance of thorough input validation in kernel space code and demonstrates how seemingly minor implementation flaws can lead to severe system compromise. Regular security audits of kernel components and adherence to security best practices for file system implementations can help prevent similar vulnerabilities from being introduced in future code releases.