CVE-2016-10088 in Linux
Summary
by MITRE
The sg implementation in the Linux kernel through 4.9 does not properly restrict write operations in situations where the KERNEL_DS option is set, which allows local users to read or write to arbitrary kernel memory locations or cause a denial of service (use-after-free) by leveraging access to a /dev/sg device, related to block/bsg.c and drivers/scsi/sg.c. NOTE: this vulnerability exists because of an incomplete fix for CVE-2016-9576.
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Analysis
by VulDB Data Team • 10/27/2022
The vulnerability described in CVE-2016-10088 represents a critical security flaw in the Linux kernel's SCSI generic (sg) device driver implementation that affects kernel versions through 4.9. This issue stems from inadequate restrictions on write operations when the KERNEL_DS option is enabled, creating a dangerous privilege escalation vector for local attackers who possess access to the /dev/sg device. The vulnerability is particularly concerning because it builds upon and fails to fully address the previously identified CVE-2016-9576, indicating a pattern of incomplete security remediation that leaves systems exposed to sophisticated attack vectors. The sg device driver interface is commonly used by applications that need to communicate with SCSI devices, making this vulnerability accessible to any user who can open and interact with the generic SCSI device.
The technical root cause of this vulnerability lies in the improper handling of memory access controls within the block/bsg.c and drivers/scsi/sg.c kernel source files. When KERNEL_DS is set, the kernel's data segment protection mechanisms are bypassed, allowing the sg driver to perform operations that should be restricted to kernel-level code only. This creates a scenario where a local attacker can manipulate the device driver to read or write to arbitrary kernel memory addresses, effectively breaking the kernel's memory protection boundaries. The flaw specifically manifests during write operations where the kernel fails to validate the memory addresses being accessed, leading to potential information disclosure, arbitrary code execution, or system instability. The vulnerability's classification as a use-after-free condition indicates that memory that has been freed may still be accessible, creating additional attack surfaces for exploitation.
The operational impact of CVE-2016-10088 extends beyond simple privilege escalation, as it can result in complete system compromise when exploited by malicious local users. Attackers can leverage this vulnerability to read sensitive kernel memory regions containing credentials, cryptographic keys, or other confidential information, while also potentially writing malicious code directly into kernel space to maintain persistence. The denial of service aspect of this vulnerability means that systems may become unstable or crash when the flawed code path is triggered, potentially affecting system availability. Given that the /dev/sg device is often accessible to userspace applications for legitimate SCSI operations, the attack surface is broader than initially apparent, as many system administration tools and applications may require access to these devices. This vulnerability particularly affects systems running kernel versions 4.9 and earlier, where the incomplete fix for CVE-2016-9576 leaves the underlying memory access control mechanisms vulnerable to exploitation.
Organizations should prioritize immediate patching of affected systems to address this vulnerability, as it represents a serious threat to system integrity and security. The recommended mitigation strategy involves upgrading to kernel versions that contain complete fixes for both CVE-2016-10088 and CVE-2016-9576, ensuring that all memory access controls are properly enforced. System administrators should also implement additional monitoring to detect unauthorized access to /dev/sg devices and consider restricting access to these devices to only trusted users and applications. From a compliance perspective, this vulnerability relates to CWE-121, which addresses buffer overflow conditions, and aligns with ATT&CK techniques focused on privilege escalation and kernel exploitation. Organizations should also consider implementing kernel module signing and lockdown mechanisms to further protect against unauthorized kernel memory access and ensure that only verified, trusted code can execute with kernel privileges.