CVE-2024-50080 in Linux
Summary
by MITRE • 10/29/2024
In the Linux kernel, the following vulnerability has been resolved:
ublk: don't allow user copy for unprivileged device
UBLK_F_USER_COPY requires userspace to call write() on ublk char device for filling request buffer, and unprivileged device can't be trusted.
So don't allow user copy for unprivileged device.
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Analysis
by VulDB Data Team • 10/02/2025
The vulnerability identified as CVE-2024-50080 resides within the Linux kernel's ublk (user block) subsystem, representing a critical privilege escalation risk that undermines the security boundaries between privileged and unprivileged device operations. This issue specifically affects the ublk character device implementation where the UBLK_F_USER_COPY flag enables userspace processes to directly manage request buffer filling through write() system calls. The flaw demonstrates a fundamental misalignment in access control mechanisms, as it permits potentially malicious unprivileged processes to manipulate kernel memory regions through carefully crafted buffer operations that should only be accessible to privileged kernel components.
The technical implementation of this vulnerability stems from the ublk subsystem's design where the UBLK_F_USER_COPY flag creates a pathway for userspace to directly participate in kernel memory management operations. When this flag is enabled, userspace applications can invoke write() operations on the ublk character device to populate request buffers, effectively bridging the gap between user and kernel memory spaces. This mechanism, while intended to provide flexibility in block device implementations, creates a dangerous attack surface when applied to unprivileged device contexts where the kernel cannot properly validate or trust the integrity of user-supplied data. The vulnerability manifests when unprivileged processes gain access to ublk devices that have the user copy flag enabled, allowing them to potentially manipulate kernel memory structures through crafted write operations.
The operational impact of CVE-2024-50080 extends beyond simple privilege escalation to encompass potential system compromise and data integrity violations. An unprivileged attacker who gains access to a ublk device with user copy capabilities could leverage this vulnerability to execute arbitrary code within kernel space, potentially leading to full system compromise. The attack vector relies on the attacker's ability to either directly access the ublk device or exploit a privilege escalation path that grants access to such devices. This vulnerability directly violates the principle of least privilege and undermines the kernel's memory safety mechanisms, as it allows userspace processes to bypass kernel security checks that should prevent direct manipulation of kernel memory regions. The implications align with CWE-276, which addresses improper privilege management, and can be mapped to ATT&CK technique T1068, involving privilege escalation through kernel exploits.
Mitigation strategies for CVE-2024-50080 require immediate implementation of kernel patches that enforce strict access controls on ublk devices with user copy capabilities. The recommended approach involves modifying the kernel's ublk subsystem to completely disable user copy operations for unprivileged devices, ensuring that only properly authenticated and privileged processes can utilize this functionality. System administrators should implement comprehensive monitoring of ublk device access patterns and establish strict device permissions that prevent unauthorized access to potentially vulnerable ublk interfaces. Additionally, the kernel configuration should be reviewed to ensure that ublk subsystem components are appropriately restricted based on user privileges, with the patch ensuring that unprivileged device contexts cannot be configured to use the UBLK_F_USER_COPY flag. This remediation aligns with the principle of defense in depth and addresses the core architectural flaw that enables the vulnerability while maintaining legitimate functionality for privileged users who require such capabilities for legitimate system operations.