Out-of-bounds read in Linux kernel - CVE-2026-64186

Vulnerability identifier: #VU138428

CSH Severity: Low

CVSS v4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-64186

CWE-ID: CWE-125

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to perform an out-of-bounds memory access.

The vulnerability exists due to an out-of-bounds access in AMD IOMMU debugfs handlers when parsing user-supplied debugfs offset values. A local user can provide a sufficiently large value that becomes negative to perform an out-of-bounds memory access.

The issue affects the iommu_mmio_write() and iommu_capability_write() paths in the AMD IOMMU debugfs interface.

Linux kernel
Ubuntu
linux-ibm (Ubuntu package)
linux-azure (Ubuntu package)
linux-aws (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-nvidia-bos (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux-ibm (Ubuntu package) - addressed in versions 7.0.0-1008.8, 7.0.0-1010.10
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1010.10
linux-aws (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1015.15
linux-nvidia (Ubuntu package) - addressed in versions 7.0.0-1016.16, 7.0.0-1016.16~24.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2016.16

• https://git.kernel.org/stable/c/488d2c76bd9f78433a70690d1054bfae3d39a407
• https://git.kernel.org/stable/c/62f9dfbf1aceae88b03c5ca08f7d36e943939dec
• https://git.kernel.org/stable/c/8dfd3d8d74435344ee8dc9237596959c8b2a6cbe

• Out-of-bounds read in Linux kernel iommu amd driver
• Ubuntu update for linux-ibm
• Ubuntu update for linux-azure
• Ubuntu update for linux-aws
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia