Linux Kernel up to 6.12.82/6.18.23/6.19.13/7.0.0 __copy_user_nocache buffer overflow

CVSS Meta Temp Score
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CTI Interest Score
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6.6$0-$5k0.00

Summaryinfo

A vulnerability identified as critical has been detected in Linux Kernel up to 6.12.82/6.18.23/6.19.13/7.0.0. This affects the function __copy_user_nocache. Performing a manipulation results in buffer overflow. This vulnerability is cataloged as CVE-2026-43073. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.12.82/6.18.23/6.19.13/7.0.0. This affects the function __copy_user_nocache. The manipulation with an unknown input leads to a buffer overflow vulnerability. CWE is classifying the issue as CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-43073 since 05/01/2026. The exploitability is told to be easy. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/08/2026).

The vulnerability scanner Nessus provides a plugin with the ID 312299 (Linux Distros Unpatched Vulnerability : CVE-2026-43073), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.12.83, 6.18.24, 6.19.14, 7.0.1 or 7.1-rc1 eliminates this vulnerability. Applying the patch 14b9194db4a28421a4dbe5d6e519efbaa7c5f3cd/c6d4e0599e7e73abc04e2488dfeb7940c4039660/d993e1723aa2a085aa0d72e70ea889031fc225b4/efea91ad1729ff1853d7418e4d3bc27d085e72d0/d187a86de793f84766ea40b9ade7ac60aabbb4fe is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (312299) and CERT Bund (WID-SEC-2026-1385). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • Open Source Linux Kernel
  • RESF Rocky Linux
  • Microsoft Azure Linux

Productinfo

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Version

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Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.8
VulDB Meta Temp Score: 6.6

VulDB Base Score: 8.0
VulDB Temp Score: 7.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Buffer overflow
CWE: CWE-120 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 312299
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-43073

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.12.83/6.18.24/6.19.14/7.0.1/7.1-rc1
Patch: 14b9194db4a28421a4dbe5d6e519efbaa7c5f3cd/c6d4e0599e7e73abc04e2488dfeb7940c4039660/d993e1723aa2a085aa0d72e70ea889031fc225b4/efea91ad1729ff1853d7418e4d3bc27d085e72d0/d187a86de793f84766ea40b9ade7ac60aabbb4fe

Timelineinfo

05/01/2026 CVE reserved
05/05/2026 +4 days Advisory disclosed
05/05/2026 +0 days VulDB entry created
06/08/2026 +34 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-43073 (🔒)
GCVE (CVE): GCVE-0-2026-43073
GCVE (VulDB): GCVE-100-361209
CERT Bund: WID-SEC-2026-1385 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 05/05/2026 19:40
Updated: 06/08/2026 14:51
Changes: 05/05/2026 19:40 (58), 05/06/2026 14:05 (2), 05/07/2026 03:05 (7), 06/07/2026 12:52 (11), 06/08/2026 14:51 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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