CVE-2026-68259 Overview
CVE-2026-68259 is a missing bounds check vulnerability in the Linux kernel's AMD Kernel Fusion Driver (amdkfd), specifically within the allocate_event_notification_slot function. The function accepts a caller-specified event id used by Checkpoint/Restore In Userspace (CRIU) but did not validate that value against KFD_SIGNAL_EVENT_LIMIT. An out-of-bounds event id could be passed through the graphics/compute event allocation path. Maintainers resolved the issue by adding an upper bounds check against KFD_SIGNAL_EVENT_LIMIT; the lower bound is already enforced by idr_alloc, which rejects negative values.
Critical Impact
Local callers with access to the AMD KFD interface could supply an event id outside the valid range, exposing the kernel to out-of-bounds behavior in the event notification path on affected AMD GPU-enabled Linux systems.
Affected Products
- Linux kernel builds shipping the drm/amdkfd driver prior to the fix
- Distributions and stable trees receiving the cherry-pick of upstream commit 6853f1f6cbbe
- Systems using AMD KFD with CRIU checkpoint/restore workflows
Discovery Timeline
- 2026-08-10 - CVE-2026-68259 published to NVD
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-68259
Vulnerability Analysis
The AMD Kernel Fusion Driver (amdkfd) provides compute event signaling for GPU workloads. The allocate_event_notification_slot function can allocate a slot at an event id specified by the caller, a path exercised by CRIU during process checkpoint and restore. Before the fix, the function did not validate the supplied event id against KFD_SIGNAL_EVENT_LIMIT, the upper limit of valid ids. A value above this limit could reach the underlying allocation logic even though signal mode mappings for that id may not yet exist, producing out-of-bounds behavior in kernel memory tied to event notification.
Root Cause
The root cause is missing input validation [CWE-20] on the event_id parameter accepted by allocate_event_notification_slot. The upstream fix adds an explicit upper bounds check against KFD_SIGNAL_EVENT_LIMIT. A lower bounds check is unnecessary because idr_alloc already rejects negative values. The change was applied via cherry-pick of commit 6853f1f6cbbeb3f53ebbbd7286536aeb2c5d5f50 and propagated across stable branches in commits 4622214f, 50319efb, 85eedff5, abeeb194, and bb52249f.
Attack Vector
An attacker requires local access with permission to interact with the AMD KFD device interface, typically through the compute stack or a CRIU-driven restore operation. By supplying an event id above KFD_SIGNAL_EVENT_LIMIT, the caller could drive the driver into an out-of-bounds state in the notification slot handling path. The vulnerability does not expose a network-reachable attack surface. Refer to the Linux Kernel Commit 4622214 and related stable-tree commits for the exact code change.
Detection Methods for CVE-2026-68259
Indicators of Compromise
- Unexpected kernel log entries or oops messages originating from amdkfd event handling on systems with AMD GPUs.
- CRIU checkpoint or restore operations invoking KFD event allocation with event ids at or near KFD_SIGNAL_EVENT_LIMIT.
Detection Strategies
- Inventory kernel versions across Linux hosts and compare against the patched stable-tree commits referenced above.
- Audit workloads that use AMD KFD compute events, particularly CRIU-based checkpoint/restore pipelines, for anomalous event id values.
- Correlate kernel ring buffer (dmesg) telemetry for amdkfd warnings with process activity to identify local abuse attempts.
Monitoring Recommendations
- Forward journalctl -k and /var/log/kern.log streams to a centralized log platform and alert on amdkfd errors.
- Monitor for unauthorized loading or interaction with the amdgpu/amdkfd modules on systems that do not require GPU compute.
- Track EPSS scoring (currently 0.168%) alongside vendor advisories to reprioritize if exploit activity emerges.
How to Mitigate CVE-2026-68259
Immediate Actions Required
- Apply the patched Linux kernel from your distribution once it incorporates upstream commit 6853f1f6cbbe or one of the stable-tree cherry-picks.
- Restrict local access to the AMD KFD device nodes to trusted users and service accounts only.
- Inventory hosts running AMD GPUs used for compute or CRIU workflows and prioritize them for kernel updates.
Patch Information
The fix adds an upper bounds check against KFD_SIGNAL_EVENT_LIMIT inside allocate_event_notification_slot. It is available in the following stable-tree commits: Linux Kernel Commit 4622214, Linux Kernel Commit 50319ef, Linux Kernel Commit 85eedff, Linux Kernel Commit abeeb19, and Linux Kernel Commit bb52249.
Workarounds
- Where GPU compute is not required, unload or blocklist the amdkfd module until a patched kernel is deployed.
- Constrain permissions on /dev/kfd and related device files so only authorized users can invoke event allocation paths.
- Pause or isolate CRIU-based checkpoint/restore workflows against unpatched AMD KFD hosts until the fix is applied.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
