CVE-2010-2521 in Linux
Summary
by MITRE
Multiple buffer overflows in fs/nfsd/nfs4xdr.c in the XDR implementation in the NFS server in the Linux kernel before 2.6.34-rc6 allow remote attackers to cause a denial of service (panic) or possibly execute arbitrary code via a crafted NFSv4 compound WRITE request, related to the read_buf and nfsd4_decode_compound functions.
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Analysis
by VulDB Data Team • 12/29/2024
The vulnerability identified as CVE-2010-2521 represents a critical buffer overflow flaw within the Linux kernel's Network File System version 4 implementation. This issue resides in the XDR (External Data Representation) parsing code located in fs/nfsd/nfs4xdr.c, specifically affecting the nfsd4_decode_compound function and related read_buf handling mechanisms. The flaw manifests when processing crafted NFSv4 compound WRITE requests, which are legitimate network operations used by clients to write data to files through the NFS server. The vulnerability stems from insufficient bounds checking during the decoding process of compound operations, where the server fails to properly validate the size of incoming data buffers before attempting to copy data into fixed-size internal buffers. This allows malicious actors to craft specially formatted requests that exceed the allocated buffer space, leading to memory corruption that can result in system crashes or potentially arbitrary code execution.
The technical exploitation of this vulnerability involves sending a malformed NFSv4 compound WRITE request that triggers the buffer overflow condition during XDR decoding. When the nfsd4_decode_compound function processes the malicious request, it attempts to copy data into internal buffers without adequate size validation, causing the buffer to overflow and overwrite adjacent memory regions. The attack vector is remote and requires no authentication, making it particularly dangerous as it can be exploited by any network-connected client capable of communicating with the NFS server. The flaw affects all Linux kernel versions prior to 2.6.34-rc6, representing a significant window of vulnerable systems that could be targeted by attackers. The buffer overflow occurs in the context of the kernel's network service handling, meaning that successful exploitation can lead to system panics, complete system crashes, or in some cases, provide attackers with elevated privileges through kernel memory corruption.
The operational impact of CVE-2010-2521 extends beyond simple denial of service scenarios, as the vulnerability presents potential for remote code execution in certain configurations. The buffer overflow can cause the kernel to panic and reboot the affected system, creating availability issues that can disrupt critical services relying on NFS storage. However, the more concerning aspect is the potential for arbitrary code execution, which would allow attackers to gain control of the system and execute malicious code with kernel-level privileges. This makes the vulnerability particularly attractive to attackers seeking to establish persistent access to networked systems. The vulnerability affects any system running an affected Linux kernel version with NFSv4 services enabled, including enterprise servers, storage appliances, and cloud infrastructure components. Organizations with widespread NFS deployments face significant risk, as the vulnerability can be exploited by attackers who gain network access to the NFS server, potentially leading to data compromise and system takeover.
Mitigation strategies for CVE-2010-2521 primarily focus on immediate kernel upgrades to versions 2.6.34-rc6 or later where the vulnerability has been patched. System administrators should prioritize updating all NFS server implementations to the latest stable kernel releases, ensuring that the patched code properly validates buffer sizes during XDR decoding operations. Additionally, network segmentation and access control measures should be implemented to limit exposure of NFS services to untrusted networks. The patch addresses the core issue by adding proper bounds checking in the read_buf and nfsd4_decode_compound functions, preventing the buffer overflow condition from occurring. Organizations should also implement monitoring to detect unusual NFS traffic patterns that might indicate exploitation attempts, as well as consider disabling NFSv4 if the service is not required. From a security framework perspective, this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and maps to ATT&CK technique T1059.007 for execution through kernel modules, highlighting the need for kernel-level security controls and privilege separation measures to prevent exploitation.