CVE-2026-46064
Awaiting Analysis Awaiting Analysis - Queue
Heap Over-Read in Linux Kernel ibmasm Driver

Publication date: 2026-05-27

Last updated on: 2026-06-01

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ibmasm: fix heap over-read in ibmasm_send_i2o_message() The ibmasm_send_i2o_message() function uses get_dot_command_size() to compute the byte count for memcpy_toio(), but this value is derived from user-controlled fields in the dot_command_header (command_size: u8, data_size: u16) and is never validated against the actual allocation size. A root user can write a small buffer with inflated header fields, causing memcpy_toio() to read up to ~65 KB past the end of the allocation into adjacent kernel heap, which is then forwarded to the service processor over MMIO. Silently clamping the copy size is not sufficient: if the header fields claim a larger size than the buffer, the SP receives a dot command whose own header is inconsistent with the I2O message length, which can cause the SP to desynchronize. Reject such commands outright by returning failure. Validate command_size before calling get_mfa_inbound() to avoid leaking an I2O message frame: reading INBOUND_QUEUE_PORT dequeues a hardware frame from the controller's free pool, and returning without a corresponding set_mfa_inbound() call would permanently exhaust it. Additionally, clamp command_size to I2O_COMMAND_SIZE before the memcpy_toio() so the MMIO write stays within the I2O message frame, consistent with the clamping already performed by outgoing_message_size() for the header field.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-05-27
Last Modified
2026-06-01
Generated
2026-06-16
AI Q&A
2026-05-27
EPSS Evaluated
2026-06-15
NVD
CVE-2026-46064
EUVD
EUVD-2026-32446
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
ibm ibmasm *
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Executive Summary

This vulnerability exists in the Linux kernel's ibmasm component, specifically in the ibmasm_send_i2o_message() function. The function uses user-controlled fields from a dot_command_header to determine the size of a memory copy operation without properly validating these sizes against the actual buffer allocation.

A root user can exploit this by crafting a small buffer with inflated header size fields, causing the function to read up to approximately 65 KB beyond the allocated buffer into adjacent kernel heap memory. This over-read data is then sent to the service processor over MMIO.

The vulnerability can cause the service processor to receive inconsistent command headers, potentially leading to desynchronization. The fix involves rejecting commands with invalid sizes outright and clamping the copy size to prevent reading beyond the allocated message frame.

Impact Analysis

This vulnerability can lead to a heap over-read in the kernel, allowing a root user to read sensitive kernel memory beyond the intended buffer. This could expose sensitive information stored in adjacent kernel heap memory.

Additionally, the corrupted or inconsistent messages sent to the service processor may cause it to desynchronize, potentially impacting system stability or the correct functioning of hardware communication.

Mitigation Strategies

To mitigate this vulnerability, ensure that the Linux kernel version you are using includes the fix for the ibmasm_send_i2o_message() function.

The fix involves rejecting commands with inconsistent or inflated header fields outright by returning failure, validating command_size before processing to avoid leaking I2O message frames, and clamping command_size to the maximum allowed size before memory operations.

Therefore, immediate steps include updating your Linux kernel to a version that contains these patches to prevent heap over-read and potential service processor desynchronization.

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-46064. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart