CVE-2011-4324 in Linux
Summary
by MITRE
The encode_share_access function in fs/nfs/nfs4xdr.c in the Linux kernel before 2.6.29 allows local users to cause a denial of service (BUG and system crash) by using the mknod system call with a pathname on an NFSv4 filesystem.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 12/05/2021
The vulnerability identified as CVE-2011-4324 represents a critical flaw in the Linux kernel's handling of NFSv4 filesystem operations, specifically within the encode_share_access function located in fs/nfs/nfs4xdr.c. This issue affects Linux kernel versions prior to 2.6.29 and demonstrates a classic buffer overflow condition that can be exploited to trigger system instability. The vulnerability manifests when local users execute the mknod system call with a specially crafted pathname on an NFSv4 mounted filesystem, leading to unpredictable system behavior including kernel panics and complete system crashes. The technical implementation involves improper validation of share access parameters during NFSv4 protocol handling, where the encode_share_access function fails to properly bounds-check input data before processing it within the kernel's network file system subsystem.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged by malicious local users to disrupt system availability and potentially compromise the stability of networked file services. When exploited, the vulnerability causes the kernel to enter an unrecoverable state where it encounters a BUG condition and subsequently crashes the entire system. This behavior aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a serious security risk in environments where local users might have access to NFSv4 filesystems. The attack vector requires local system access but can be particularly damaging in multi-user environments or when the affected system serves critical network services through NFSv4. From an adversary perspective, this vulnerability maps to ATT&CK technique T1499.004, which involves network denial of service attacks, though the specific implementation targets local privilege escalation and system stability rather than network-based attacks.
Mitigation strategies for CVE-2011-4324 primarily focus on kernel version updates, as the vulnerability was addressed in kernel versions 2.6.29 and later through proper bounds checking in the encode_share_access function. System administrators should prioritize patching affected systems, particularly those running NFSv4 services where local users might exist. Additional protective measures include restricting local user access to NFSv4 filesystems where possible, implementing proper access controls, and monitoring for unusual mknod system call patterns. Organizations should also consider implementing network segmentation to limit exposure and ensure that NFSv4 services are not running with unnecessary privileges. The vulnerability highlights the importance of proper input validation in kernel space operations and demonstrates how seemingly minor flaws in protocol handling can lead to complete system compromise, making it essential for security teams to maintain up-to-date kernel versions and conduct regular vulnerability assessments of their network infrastructure components.