CVE-2026-43073x86-64: rename misleadingly named '__copy_user_nocache()' function

Description

In the Linux kernel, the following vulnerability has been resolved: x86-64: rename misleadingly named '__copy_user_nocache()' function This function was a masterclass in bad naming, for various historical reasons. It claimed to be a non-cached user copy. It is literally _neither_ of those things. It's a specialty memory copy routine that uses non-temporal stores for the destination (but not the source), and that does exception handling for both source and destination accesses. Also note that while it works for unaligned targets, any unaligned parts (whether at beginning or end) will not use non-temporal stores, since only words and quadwords can be non-temporal on x86. The exception handling means that it _can_ be used for user space accesses, but not on its own - it needs all the normal "start user space access" logic around it. But typically the user space access would be the source, not the non-temporal destination. That was the original intention of this, where the destination was some fragile persistent memory target that needed non-temporal stores in order to catch machine check exceptions synchronously and deal with them gracefully. Thus that non-descriptive name: one use case was to copy from user space into a non-cached kernel buffer. However, the existing users are a mix of that intended use-case, and a couple of random drivers that just did this as a performance tweak. Some of those random drivers then actively misused the user copying version (with STAC/CLAC and all) to do kernel copies without ever even caring about the exception handling, _just_ for the non-temporal destination. Rename it as a first small step to actually make it halfway sane, and change the prototype to be more normal: it doesn't take a user pointer unless the caller has done the proper conversion, and the argument size is the full size_t (it still won't actually copy more than 4GB in one go, but there's also no reason to silently truncate the size argument in the caller). Finally, use this now sanely named function in the NTB code, which mis-used a user copy version (with STAC/CLAC and all) of this interface despite it not actually being a user copy at all.

Timeline

Scores

EPSS (exploitation in 30 days)

0.16% · top 95% of all CVEs (15 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.

Affected products

• Linux · Linux

  • affected 06917f753547e6bba8a5d17f79971d1c071a70dd – < 73c2dc2c14d6a2efa5dde469546a907482af07fe
  • affected 06917f753547e6bba8a5d17f79971d1c071a70dd – < 14b9194db4a28421a4dbe5d6e519efbaa7c5f3cd
  • affected 06917f753547e6bba8a5d17f79971d1c071a70dd – < c6d4e0599e7e73abc04e2488dfeb7940c4039660
  • affected 06917f753547e6bba8a5d17f79971d1c071a70dd – < d993e1723aa2a085aa0d72e70ea889031fc225b4
  • affected 06917f753547e6bba8a5d17f79971d1c071a70dd – < efea91ad1729ff1853d7418e4d3bc27d085e72d0
  • affected 06917f753547e6bba8a5d17f79971d1c071a70dd – < d187a86de793f84766ea40b9ade7ac60aabbb4fe

• Linux · Linux

  • affected 4.2
  • unaffected < 4.2
  • unaffected 6.6.160 – ≤ 6.6.*
  • unaffected 6.12.83 – ≤ 6.12.*
  • unaffected 6.18.24 – ≤ 6.18.*
  • unaffected 6.19.14 – ≤ 6.19.*
  • unaffected 7.0.1 – ≤ 7.0.*
  • unaffected 7.1 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-27378 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-43073](https://cveledger.app/badge/CVE-2026-43073.svg)](https://cveledger.app/cve/CVE-2026-43073)

Record last updated 6 Nov 2026, 15:32 UTC.