CVE-2011-5327 in Linux
Summary
by MITRE
In the Linux kernel before 3.1, an off by one in the drivers/target/loopback/tcm_loop.c tcm_loop_make_naa_tpg() function could result in at least memory corruption.
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Analysis
by VulDB Data Team • 11/13/2023
The vulnerability described in CVE-2011-5327 represents a critical memory corruption flaw within the Linux kernel's target core subsystem, specifically affecting the tcm_loop driver implementation. This issue resides in the drivers/target/loopback/tcm_loop.c file where the tcm_loop_make_naa_tpg() function contains an off-by-one error that can lead to unauthorized memory access patterns. The vulnerability manifests when processing NAA (Name Address Authority) target port groups, which are fundamental components in storage area network (SAN) configurations where the Linux kernel acts as a target device for iSCSI or other storage protocols. The affected kernel versions prior to 3.1 represent a significant security gap that could be exploited by malicious actors with access to the system or through carefully crafted network requests that trigger the vulnerable code path.
The technical nature of this flaw stems from improper boundary checking within the memory allocation and string handling operations of the tcm_loop_make_naa_tpg() function. An off-by-one error typically occurs when loop counters or array indices are incorrectly calculated, leading to one additional iteration or access beyond the allocated memory boundaries. In this specific case, the vulnerability allows attackers to write beyond the intended memory allocation for NAA identifiers, potentially corrupting adjacent memory regions. This type of error falls under the CWE-121 category of "Stack-based Buffer Overflow" and is classified as a memory safety issue that can result in arbitrary code execution or system instability. The flaw is particularly dangerous because it operates within kernel space where memory corruption can lead to complete system compromise rather than simple application crashes.
The operational impact of CVE-2011-5327 extends beyond simple memory corruption, as it provides potential attack vectors for privilege escalation and system compromise. Systems running vulnerable kernel versions that utilize the target core functionality for storage services become susceptible to exploitation by attackers who can craft specific NAA identifier structures to trigger the memory corruption. The vulnerability can be exploited through legitimate storage protocol interactions, making it particularly concerning for enterprise storage environments where the Linux kernel serves as a target device for iSCSI or other storage protocols. Attackers could potentially leverage this flaw to execute arbitrary code with kernel privileges, leading to complete system takeover, data exfiltration, or denial of service conditions that would affect storage availability and integrity. Organizations using Linux systems in storage server roles, particularly those implementing iSCSI target functionality, face significant risk from this vulnerability.
Mitigation strategies for CVE-2011-5327 primarily focus on immediate kernel version upgrades to 3.1 or later, which contain the necessary patches to address the off-by-one error in the tcm_loop driver. System administrators should prioritize updating their kernel versions and performing thorough testing to ensure compatibility with existing storage configurations. Additional defensive measures include implementing network segmentation to limit access to storage services, disabling unnecessary target core functionality when not required, and monitoring for suspicious storage protocol interactions that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.007 for execution through kernel modules and T1068 for privilege escalation through kernel vulnerabilities. Organizations should also consider implementing kernel hardening measures such as stack canaries, address space layout randomization, and kernel module signing to reduce the effectiveness of potential exploitation attempts. Regular security audits of storage configurations and kernel components remain essential for maintaining system integrity against similar memory safety vulnerabilities that could be present in other kernel subsystems.