CVE-2026-68324: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-68324 Overview

CVE-2026-68324 is an out-of-bounds write vulnerability in the Linux kernel's Intel IOMMU (Input-Output Memory Management Unit) subsystem. The flaw resides in the dmar_latency_disable() function, which was designed to zero out a single latency_statistic entry for a given type. Due to an incorrect memset size calculation, the function instead clears the entire array starting from the target index, corrupting adjacent memory. The upstream Linux kernel maintainers have addressed the issue across multiple stable branches. This vulnerability is tracked under [CWE-787: Out-of-bounds Write].

Critical Impact
When dmar_latency_disable() is invoked with a type value greater than zero, the miscalculated memset writes beyond the allocated latency_statistic array, corrupting adjacent kernel memory and potentially destabilizing the system.

Affected Products

Linux kernel builds using the Intel IOMMU driver (drivers/iommu/intel/)
Systems with DMAR (DMA Remapping) latency statistics enabled
Multiple stable kernel branches referenced in the upstream fix commits

Discovery Timeline

2026-08-10 - CVE-2026-68324 published to NVD
2026-08-10 - Last updated in NVD database

Technical Details for CVE-2026-68324

Vulnerability Analysis

The vulnerability affects the Intel IOMMU driver's DMAR latency tracking subsystem in the Linux kernel. The dmar_latency_disable() function is intended to reset statistics for a specific latency measurement type by zeroing a single latency_statistic structure within an array indexed by type. Instead, the buggy implementation multiplies the per-entry size by DMAR_LATENCY_NUM, causing the memset operation to clear a region equal to the entire array length beginning at the offset of the requested type. When the caller supplies any type value greater than zero, the write extends past the last valid element of the array and overwrites adjacent kernel memory with zeros.

Root Cause

The root cause is an incorrect size argument passed to memset. The developer used sizeof(*lstat) * DMAR_LATENCY_NUM when only sizeof(*lstat) was needed to clear the single target entry. The fix, applied across the referenced stable commits, replaces the miscomputed length with sizeof(*lstat) so only the intended element is cleared.

Attack Vector

The vulnerability requires reaching dmar_latency_disable() with a non-zero type argument. This is a local, kernel-context issue and the resulting memory corruption manifests as zeroed bytes written past the end of the latency_statistic array. The consequences depend on what data structures reside adjacent to the array in kernel memory, and can range from silent state corruption to kernel instability. No public exploit is available and no in-the-wild exploitation has been reported.

For implementation-level details, see the upstream fix commits: Kernel Git Commit 0e28ca1, Kernel Git Commit 3078d82, Kernel Git Commit 754f8ef, Kernel Git Commit 866a357, and Kernel Git Commit d06fea9.

Detection Methods for CVE-2026-68324

Indicators of Compromise

Unexpected kernel oops, panics, or slab corruption warnings referencing the Intel IOMMU (intel-iommu, dmar) subsystem.
Kernel log entries showing corruption or use-after-free style faults following DMAR latency configuration changes via debugfs.
Anomalous zeroing of kernel data structures allocated near latency_statistic arrays.

Detection Strategies

Inventory kernel versions across Linux hosts and flag builds that predate the referenced stable fix commits.
Monitor dmesg and journald for KASAN, slab, or IOMMU-related warnings on systems using Intel VT-d.
Correlate host telemetry from EDR agents with kernel version data to prioritize unpatched hosts.

Monitoring Recommendations

Ingest kernel logs into a centralized SIEM and alert on IOMMU/DMAR fault patterns.
Track configuration changes to DMAR debugfs interfaces that toggle latency statistics.
Establish a baseline of expected kernel versions and alert on drift from patched baselines.

How to Mitigate CVE-2026-68324

Immediate Actions Required

Update affected Linux systems to a kernel version that incorporates the upstream fix referenced in the stable commits.
Prioritize patching on hosts that expose Intel IOMMU latency debugfs interfaces to non-root users or automation.
Validate distribution vendor advisories (RHEL, Ubuntu, SUSE, Debian) for backported package versions.

Patch Information

The fix replaces sizeof(*lstat) * DMAR_LATENCY_NUM with sizeof(*lstat) in dmar_latency_disable(), restricting the memset to a single array entry. Backports are available in the upstream stable trees via the commits referenced above.

Workarounds

Avoid triggering dmar_latency_disable() with a non-zero type value until a patched kernel is installed.
Restrict access to DMAR-related debugfs entries so that only trusted administrative accounts can modify latency statistics.
Where feasible, disable DMAR latency statistics collection until patched kernels are deployed.

bash

# Verify running kernel version and restrict debugfs access
uname -r
mount -o remount,mode=700 /sys/kernel/debug