Out-of-Bounds Read in Linux kernel (CVE-2026-64186)
Summary
Vulnerability in Linux kernel (CVE-2026-64186). Confidential information can be exposed externally.
Original description
The description as published by the source.
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.
- #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;
- 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;
- 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().
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-64186 has been found in Linux kernel.
Confidential information can be exposed externally. CVSS score: 7.1/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-64186" on the vendor's site.
CVE-2026-64186 (Linux kernel) — CWE-125 / CVSS v3 7.1
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Out-of-bounds read (CWE-125) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.1/10). Confidential information can be exposed externally.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-64186 linux-lts Fixed in: 6.18.35-r1
- Debian DEBIAN-CVE-2026-64186 linux Fixed in: 7.0.12-1
- Ubuntu UBUNTU-CVE-2026-64186 linux-hwe-edge
References
- advisory nvd.nist.gov
- advisory github.com
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web github.com