CVE-2026-23149 in Linux
Summary
by MITRE • 02/14/2026
In the Linux kernel, the following vulnerability has been resolved:
drm: Do not allow userspace to trigger kernel warnings in drm_gem_change_handle_ioctl()
Since GEM bo handles are u32 in the uapi and the internal implementation uses idr_alloc() which uses int ranges, passing a new handle larger than INT_MAX trivially triggers a kernel warning:
idr_alloc(): ... if (WARN_ON_ONCE(start < 0)) return -EINVAL; ...
Fix it by rejecting new handles above INT_MAX and at the same time make the end limit calculation more obvious by moving into int domain.
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Analysis
by VulDB Data Team • 03/18/2026
The vulnerability identified as CVE-2026-23149 resides within the Linux kernel's Direct Rendering Manager (DRM) subsystem, specifically in the drm_gem_change_handle_ioctl() function. This issue represents a kernel warning trigger that occurs when userspace applications attempt to manipulate Graphics Execution Manager (GEM) buffer object handles. The flaw stems from a fundamental mismatch between the userspace API interface and the kernel's internal implementation, creating a potential vector for denial of service or information disclosure attacks. The vulnerability manifests when a GEM buffer object handle exceeds the maximum integer value, causing unexpected kernel behavior and warning messages that could expose system internals to unauthorized parties.
The technical root cause of this vulnerability lies in the improper handling of handle values during GEM buffer object management operations. The DRM subsystem's userspace API defines GEM buffer object handles as 32-bit unsigned integers (u32), while the internal kernel implementation utilizes the idr_alloc() function which operates within signed integer ranges. This discrepancy creates a scenario where passing a handle value greater than INT_MAX (2,147,483,647) triggers the kernel's warning mechanism through the idr_alloc() function's validation logic. The specific warning condition occurs at the line where WARN_ON_ONCE(start < 0) is evaluated, which would fail when a large handle value is processed, resulting in kernel warning messages that could be exploited for system reconnaissance or to disrupt normal operations.
The operational impact of CVE-2026-23149 extends beyond simple kernel warnings, as it represents a potential denial of service vector that could be exploited by malicious userspace processes. When the kernel warning is triggered, it may cause system instability, performance degradation, or even complete system hangs depending on the implementation details. The vulnerability affects any system running a Linux kernel version containing the affected DRM code, particularly those utilizing graphics-intensive applications or systems that rely on GEM buffer object management. Additionally, the warning messages generated could potentially leak kernel memory addresses or other sensitive information that could aid attackers in developing more sophisticated exploitation techniques, making this issue particularly concerning from a security perspective.
The fix implemented for CVE-2026-23149 addresses the core issue by adding explicit validation to reject handle values exceeding INT_MAX before they can trigger the kernel warning mechanism. This approach directly aligns with security best practices by preventing invalid input from reaching the vulnerable kernel code paths. The solution also improves code clarity by moving the end limit calculation into the integer domain, making the implementation more maintainable and less prone to similar issues in the future. This fix conforms to the CWE-129 principle of input validation and aligns with the ATT&CK technique T1059.008 for execution through command and scripting interpreter, as it prevents malicious input from causing unexpected kernel behavior. The mitigation strategy follows the principle of least privilege by ensuring that userspace cannot manipulate kernel state through invalid handle values, thereby reducing the attack surface and maintaining system stability. The implementation also demonstrates adherence to the principle of fail-fast by immediately rejecting invalid inputs rather than allowing them to propagate through the system and potentially cause more serious issues.