Linux Kernel up to 6.18.33/7.0.10 AMD IOMMU iommu_mmio_write/iommu_capability_write dbg_mmio_offset/dbg_cap_offset out-of-bounds

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.18.33/7.0.10. It has been classified as very critical. Affected is the function iommu_mmio_write/iommu_capability_write of the component AMD IOMMU. The manipulation of the argument dbg_mmio_offset/dbg_cap_offset leads to out-of-bounds. This vulnerability is uniquely identified as CVE-2026-64186. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.33/7.0.10. It has been rated as very critical. This issue affects the function iommu_mmio_write/iommu_capability_write of the component AMD IOMMU. The manipulation of the argument dbg_mmio_offset/dbg_cap_offset with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: iommu/amd: Remove latent out-of-bounds access in IOMMU debugfs In iommu_mmio_write() and iommu_capability_write(), the variables dbg_mmio_offset and dbg_cap_offset are declared as int. However, they are populated using kstrtou32_from_user(). If a user provides a sufficiently large value, it can become a negative integer. Prior to this patch, the AMD IOMMU debugfs implementation was already protected by different mechanisms. 1. #define OFS_IN_SZ 8 ensures the user string <= 8 bytes, so e.g. 0xffffffff isn't a valid input. if (cnt > OFS_IN_SZ) return -EINVAL; 2. Implicit type promotion in iommu_mmio_write(), dbg_mmio_offset is int and iommu->mmio_phys_end is u64 if (dbg_mmio_offset > iommu->mmio_phys_end - sizeof(u64)) return -EINVAL; 3. The show handlers would currently catch the negative number and refuse to perform the read. Replace kstrtou32_from_user() with kstrtos32_from_user() to parse the input, and check for negative values to explicitly prevent out-of-bounds memory accesses directly in iommu_mmio_write() and iommu_capability_write().

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-64186 since 07/19/2026. The exploitation is known to be easy. The attack may be initiated remotely. Additional levels of successful authentication are required for exploitation. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/19/2026).

Upgrading to version 6.18.34 or 7.0.11 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-45871). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.18.23
• 6.18.24
• 6.18.25
• 6.18.26
• 6.18.27
• 6.18.28
• 6.18.29
• 6.18.30
• 6.18.31
• 6.18.32
• 6.18.33
• 7.0.0
• 7.0.1
• 7.0.2
• 7.0.3
• 7.0.4
• 7.0.5
• 7.0.6
• 7.0.7
• 7.0.8
• 7.0.9
• 7.0.10

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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