External risk intelligence

Linux Kernel BIOvec Merge Vulnerability.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-46115

This vulnerability exists within the Linux kernel's block layer regarding memory management and DMA mapping during I/O operations. It is a deep internal system component concerned with how memory segments are merged. It is not an internet-facing service, application, or network-reachable interface, and it cannot be triggered remotely.

Linux Kernel

6.2 to before 6.6.1406.7 to before 6.12.886.13 to before 6.18.306.19 to before 7.0.7

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This CVE identifies a flaw in the Linux kernel's memory management that could allow for improper merging of memory segments. This internal issue relates to how data is handled during I/O operations, particularly involving zone device memory.

Kernel memory merge issue identified.
Confirm relevance and exposure internally.
Understand internal system integrity.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by crafting specific memory access patterns that involve physically contiguous memory segments from different device pagemaps within the Linux kernel's block layer. This manipulation targets how the kernel decides if two memory segments can be merged, potentially leading to a state where the kernel cannot correctly track the memory's origin, resulting in a severe compromise.

Requires access to system memory operations.
Triggers when merging memory segments across pagemaps.
Risk: Data corruption, unauthorized memory access.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in the Linux kernel's block layer could affect how the system handles memory management and DMA mapping for I/O operations. When memory is registered in multiple chunks, an error in merging physically contiguous memory segments from different management structures could lead to incorrect data recovery. This issue is specific to internal system operations and requires specific conditions related to zone device memory registration and biovec merging.

System memory management integrity.
Incorrectly merging memory segments.
Potential for data corruption.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Linux kernel's block layer impacts how memory segments are merged during I/O operations. Ownership likely lies with the infrastructure or platform teams managing the Linux operating system, with the first step being to identify all Linux systems, confirm their exposure, and then plan remediation based on criticality.

Infrastructure/Platform teams own the issue.
Verify affected Linux systems and exposure.
Plan remediation based on risk assessment.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the Linux kernel?

The Linux kernel is the core component of the operating system that manages hardware resources, memory, and communication between software and physical devices. It provides essential services like file system management, process scheduling, and direct hardware interaction, serving as the foundation for servers, embedded devices, and cloud infrastructure.

What is the weakness behind CVE-2026-46115?

This vulnerability involves an issue in the kernel's block layer logic that decides if two memory segments can be combined. The kernel fails to check if these segments originate from different memory management structures, known as device pagemaps. This oversight allows it to merge segments that should remain separate, which corrupts the ability of the system to correctly identify the memory's origin during I/O operations.

How is this vulnerability triggered?

An attacker must be able to influence specific memory access patterns during I/O operations where zone device memory is involved. The issue specifically occurs when physically contiguous memory segments from different device pagemaps are incorrectly coalesced. Merging does not occur if the segments are already separated by non-contiguous boundaries, meaning standard, non-complex memory operations are not affected by this flaw.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal indicates that this vulnerability is very unlikely to be remotely reachable. Because the flaw resides in deep internal system components managing memory and DMA mapping, it does not exist as an internet-facing service or application. It requires complex, low-level internal triggers rather than typical network-based interaction.

What should I do if my systems run an affected kernel?

The primary response is to coordinate with your platform or infrastructure teams to audit your server inventory. Identify which systems are running an affected kernel version within the provided ranges. Once identified, prioritize these systems for standard kernel updates provided by your distribution vendor, which will include the necessary check to prevent improper memory merging.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.