CVE-2015-4036 in Linux
Summary
by MITRE
Array index error in the tcm_vhost_make_tpg function in drivers/vhost/scsi.c in the Linux kernel before 4.0 might allow guest OS users to cause a denial of service (memory corruption) or possibly have unspecified other impact via a crafted VHOST_SCSI_SET_ENDPOINT ioctl call. NOTE: the affected function was renamed to vhost_scsi_make_tpg before the vulnerability was announced.
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Analysis
by VulDB Data Team • 05/19/2022
The vulnerability identified as CVE-2015-4036 represents a critical array index error within the Linux kernel's virtualization subsystem, specifically affecting the vhost-scsi implementation. This flaw exists in the tcm_vhost_make_tpg function located in drivers/vhost/scsi.c, which was subsequently renamed to vhost_scsi_make_tpg in the kernel development process. The vulnerability impacts Linux kernel versions prior to 4.0, making it particularly concerning for systems running older kernel versions that are commonly found in enterprise environments and legacy deployments. The issue stems from improper validation of input parameters within the vhost_scsi_make_tpg function, which processes VHOST_SCSI_SET_ENDPOINT ioctl commands used for configuring SCSI target devices in virtualized environments.
The technical nature of this vulnerability can be categorized under CWE-129 as an "Improper Validation of Array Index" and represents a classic buffer over-read condition that occurs when the kernel fails to properly validate the size parameter provided by guest operating systems during the VHOST_SCSI_SET_ENDPOINT ioctl call. When a malicious guest OS user submits a crafted ioctl command with an invalid array index, the kernel's vhost_scsi_make_tpg function processes this input without adequate bounds checking, leading to memory corruption. This memory corruption can manifest in several ways including kernel crashes, system instability, or potentially more severe consequences depending on the specific memory locations overwritten. The vulnerability operates at the kernel level within the virtualization infrastructure, making it particularly dangerous as it can be exploited by unprivileged users within guest operating systems to compromise the host system's stability and security.
From an operational impact perspective, this vulnerability enables guest OS users to trigger a denial of service condition that can result in complete system crashes or memory corruption within the host kernel. The potential for unspecified other impacts suggests that while immediate denial of service is the most predictable outcome, there exists a possibility for more sophisticated exploitation techniques that could lead to privilege escalation or information disclosure. This vulnerability particularly affects virtualized environments where multiple guest operating systems share the same host infrastructure, as it allows one guest to potentially impact the stability and performance of other guests and the host system itself. The attack vector requires a guest operating system user to make a specific ioctl call, but the privilege level required is typically low, making this a significant concern for multi-tenant cloud environments and shared hosting platforms.
The mitigation strategy for CVE-2015-4036 involves upgrading to Linux kernel version 4.0 or later, where the vulnerability has been addressed through proper input validation and array bounds checking. System administrators should prioritize patching affected systems, particularly those running older kernel versions in production environments. Additionally, implementing proper monitoring and logging of ioctl calls can help detect potential exploitation attempts. Organizations should also consider implementing virtualization security measures such as disabling unnecessary vhost-scsi functionality when not required, and ensuring that guest operating systems have appropriate access controls and isolation measures in place. The vulnerability aligns with ATT&CK technique T1059.003 for executing malicious code through guest operating systems and represents a significant risk in cloud computing environments where guest isolation is critical for maintaining system integrity and preventing cross-tenant attacks. Organizations should also consider implementing kernel hardening measures and regularly reviewing their virtualization security configurations to minimize exposure to similar vulnerabilities.