CVE-2026-98914 in Linux
Summary
by MITRE • 10/23/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu: cap ATOM command table nesting depth
Cap nesting at 32 levels with execute_depth and return -ELOOP when exceeded.
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Analysis
by VulDB Data Team • 10/23/2026
The resolution of this vulnerability in the Linux kernel's AMD GPU driver addresses a critical flaw within the Display Manager subsystem, specifically concerning the handling of Advanced Technology Object (ATOM) command tables. These command tables are fundamental to how modern GPUs interpret firmware instructions for display configuration and power management. The core technical issue stems from an insufficient validation mechanism when processing nested ATOM commands. Previously, the kernel did not enforce a strict limit on the depth of recursion allowed during the execution of these embedded scripts. This lack of boundary checking created a scenario where maliciously crafted or malformed GPU firmware could trigger infinite or excessively deep recursive calls within the driver's command interpreter. By failing to track and restrict the nesting level, the system remained vulnerable to stack exhaustion attacks that could lead to kernel panics or denial of service conditions for local users with access to the graphics device interface.
The implemented fix introduces a hard cap on ATOM command table nesting depth, specifically limiting it to thirty-two levels. This is achieved by introducing an execute_depth counter within the driver's execution context. As each nested command is invoked, this counter increments; conversely, upon returning from a sub-command, it decrements. If the counter exceeds the predefined threshold of thirty-two during processing, the driver immediately aborts the operation and returns an error code indicating that a loop limit has been exceeded, specifically -ELOOP. This proactive validation ensures that even if malformed data attempts to exploit recursive execution paths, the kernel will safely terminate the process before stack overflow occurs. The change effectively neutralizes the attack vector by enforcing structural integrity on command sequences passed from user space or firmware interfaces into the GPU driver logic.
From an operational impact perspective, this vulnerability primarily affects local attackers who possess sufficient privileges to interact with the DRM (Direct Rendering Manager) subsystem. An attacker could potentially craft a specific sequence of ioctl calls that trigger deep nesting in ATOM commands, thereby causing a system crash or requiring a reboot. This constitutes a denial of service against the entire operating system rather than just the graphics application. The fix ensures stability and reliability for systems relying on AMD GPUs, particularly those running workloads with complex display configurations or custom firmware interactions. It also reinforces the principle of least privilege by ensuring that user-space applications cannot inadvertently or intentionally destabilize the kernel through malformed hardware commands.
This vulnerability aligns with CWE-787: Out-of-bounds Write and CWE-675: Operations on Data Uncontrolled by a Minimum Resource Limit, as it involves unbounded recursion leading to resource exhaustion. In terms of MITRE ATT&CK mapping, this relates to T1059 Command and Scripting Interpreter, where an attacker might abuse system utilities or scripts for execution, although in this specific kernel context, it is more accurately categorized under privilege escalation via local exploitation techniques that lead to denial of service. Mitigation strategies beyond the patch include ensuring that all GPU firmware images are signed and verified before loading, thereby preventing malicious code from reaching the driver layer in the first place. Additionally, administrators should keep their systems updated with the latest kernel versions containing this fix. For environments where AMD GPUs handle untrusted input or complex display setups, implementing strict monitoring of DRM subsystem logs can help detect anomalous command patterns that might indicate probing for similar vulnerabilities before they are fully exploited.