CVE-2026-68166
userfaultfd: prevent registration of special VMAs
Description
In the Linux kernel, the following vulnerability has been resolved: userfaultfd: prevent registration of special VMAs Vova Tokarev says: userfaultfd allows registration on shadow stack VMAs. With userfaultfd access, you can register on the shadow stack, discard a page ... and inject a page with chosen return addresses via UFFDIO_COPY. Update vma_can_userfault() to reject VM_SHADOW_STACK. While on it, also reject VM_SPECIAL so that if a driver would implement vm_uffd_ops, it wouldn't be possible to register special VMAs with userfaultfd. Since VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude hugetlb VMAs from the check for VM_SPECIAL.
INFO
Published Date :
Aug. 10, 2026, 1:20 p.m.
Last Modified :
Aug. 17, 2026, 5:18 a.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Update the Linux kernel to the latest version.
- Apply the patch for userfaultfd VMA registration.
- Ensure VM_SHADOW_STACK and VM_SPECIAL are rejected.
- Exclude hugetlb VMAs from the VM_SPECIAL check.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-68166.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-68166 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-68166
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-68166 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-68166 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Aug. 17, 2026
Action Type Old Value New Value Changed Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '165613191ad9d034bf17c00e3a142f9561597ec5', 'versionType': 'git'}, {'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '0c26202b157f1efc3cd2f26f5c30f59b508a6a5d', 'versionType': 'git'}, {'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '3c58f641e813c3c71039f8fd4d4e2a3aab713288', 'versionType': 'git'}], 'programFiles': ['mm/userfaultfd.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.6'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.6', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.18.44', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.6', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc5', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['mm/userfaultfd.c'], 'defaultStatus': 'affected'}] [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '165613191ad9d034bf17c00e3a142f9561597ec5', 'versionType': 'git'}, {'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '0c26202b157f1efc3cd2f26f5c30f59b508a6a5d', 'versionType': 'git'}, {'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '3c58f641e813c3c71039f8fd4d4e2a3aab713288', 'versionType': 'git'}], 'programFiles': ['mm/userfaultfd.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.6'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.6', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.18.44', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.6', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['mm/userfaultfd.c'], 'defaultStatus': 'affected'}] -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Aug. 10, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '165613191ad9d034bf17c00e3a142f9561597ec5', 'versionType': 'git'}, {'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '0c26202b157f1efc3cd2f26f5c30f59b508a6a5d', 'versionType': 'git'}, {'status': 'affected', 'version': '54007f818206dc27309ca423df4c87dd160a7208', 'lessThan': '3c58f641e813c3c71039f8fd4d4e2a3aab713288', 'versionType': 'git'}], 'programFiles': ['mm/userfaultfd.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.6'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.6', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.18.44', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.6', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc5', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['mm/userfaultfd.c'], 'defaultStatus': 'affected'}] Added Description In the Linux kernel, the following vulnerability has been resolved: userfaultfd: prevent registration of special VMAs Vova Tokarev says: userfaultfd allows registration on shadow stack VMAs. With userfaultfd access, you can register on the shadow stack, discard a page ... and inject a page with chosen return addresses via UFFDIO_COPY. Update vma_can_userfault() to reject VM_SHADOW_STACK. While on it, also reject VM_SPECIAL so that if a driver would implement vm_uffd_ops, it wouldn't be possible to register special VMAs with userfaultfd. Since VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude hugetlb VMAs from the check for VM_SPECIAL. Added Reference https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d Added Reference https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5 Added Reference https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288