CVE-2026-74713
Received Received - Intake

Buffer Overflow in Linux Kernel vhost IOTLB

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: vhost_iotlb: bound map allocation in add_range vhost_iotlb_add_range_ctx() only retires an old entry when the table has a non-zero limit, has exactly reached that limit and has VHOST_IOTLB_FLAG_RETIRE set. Non-retiring tables can keep allocating entries after reaching their configured limit. Existing vhost devices allocate their IOTLB with max_iotlb_entries from vhost.c, which defaults to 2048 and is tunable by module parameter. Use the caller-provided limit at the allocation point instead of adding a separate default in the common IOTLB helper, and reject non-positive values in vhost paths that can report an error. Other vhost IOTLB users should not create zero-limit tables when entries can be populated from userspace or guest-controlled requests. Add caller-side max_iotlb_entries parameters for mlx5 vDPA, VDUSE and vhost-vDPA. Reject non-positive VDUSE and vhost-vDPA values, and require at least two entries for vdpa_sim and mlx5 vDPA paths that install full-range mappings, since those mappings are split into two IOTLB entries. Handle full-range mappings in the common helper by checking that the IOTLB can hold both split entries before inserting the first half. This avoids returning an error after leaving a half mapping behind. When the table is full, keep the existing retire behavior for retiring tables and return -ENOSPC for non-retiring tables. Reuse the retired map node instead of freeing it and allocating a replacement, so a stream of IOTLB updates cannot keep forcing GFP_ATOMIC allocations after the table has reached its limit. If a zero-limit IOTLB still reaches the common helper, treat it as a configuration error and return -EINVAL. I found this bug myself, though the patch was written with AI assistance.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-74713
EUVD
EUVD-2026-64400

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves improper handling of IOTLB (I/O Translation Lookaside Buffer) entries in the vhost subsystem. The issue occurs when vhost_iotlb_add_range_ctx() fails to retire old entries properly, allowing allocations to exceed configured limits. This can lead to unbounded memory usage in vhost devices, potentially causing resource exhaustion or crashes.

Detection Guidance

This vulnerability is specific to the Linux kernel's vhost_iotlb implementation and does not have direct network detection methods. Detection requires checking kernel logs for IOTLB allocation errors or monitoring for excessive memory usage in vhost processes. Commands like dmesg | grep -i iotlb or journalctl -k | grep -i iotlb may reveal related errors.

Impact Analysis

If exploited, this flaw could allow a malicious guest or userspace process to trigger excessive memory allocations in the host kernel, leading to denial-of-service conditions or system instability. Systems using vhost devices with IOTLB (e.g., virtualization environments) are particularly at risk.

Mitigation Strategies

Update your Linux kernel to a patched version that includes the fix for this vulnerability. Monitor vhost processes for abnormal memory usage and ensure IOTLB limits are properly configured. If using vhost-vDPA, VDUSE, or mlx5 vDPA, verify max_iotlb_entries is set to a positive value.

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