CVE-2026-93282

Published Sep 24, 2026

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix maximum allowed access checks The DACL permission check looks for an ACE matching the current user and falls back to the Everyone ACE. It does not consider an Authenticated Users ACE, even though an authenticated session is a member of that well-known group. As a result, opening a file whose access is granted through S-1-5-11 can incorrectly fail with STATUS_ACCESS_DENIED. Treat an Authenticated Users ACE as a fallback entry alongside Everyone. The maximal access calculation also combines access masks from every ACE, regardless of whether its SID applies to the current user. This can grant rights belonging to an unrelated principal. Process only ACEs applying to the user, Everyone, or Authenticated Users, and accumulate allowed and denied masks in ACL order. Preserve explicitly requested access bits so they are validated against the resulting maximal mask. When ACCESS_SYSTEM_SECURITY is denied, report STATUS_PRIVILEGE_NOT_HELD instead of the generic STATUS_ACCESS_DENIED. Access to the system ACL requires a security privilege that ksmbd does not grant. For regular files, include FILE_EXECUTE in maximal access when the client requested GENERIC_EXECUTE and the DACL grants the complete file-read set. Keep a direct FILE_EXECUTE request subject to the explicit DACL bit. This matches the POSIX file ACL mapping without broadening specific execute requests. Do not replace rights from an applicable NT ACE with a POSIX ACL entry. The POSIX ACL is only a fallback when no user, Everyone, or Authenticated Users ACE applies; otherwise it can incorrectly broaden the stored DACL. This fixes smb2.maximum_allowed.maximum_allowed.

Is your site exposed to CVE-2026-93282?

Run a free security scan — no signup, results in seconds.

References

Frequently Asked Questions

What is CVE-2026-93282? +
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix maximum allowed access checks The DACL permission check looks for an ACE matching the current user and falls back to the Everyone ACE. It does not consider an Authenticated Users ACE, even though an authenticated session is a member of that well-known group. As a result, opening a file whose access is granted through S-1-5-11 can incorrectly fail with STATUS_ACCESS_DENIED. Treat an Authenticated Users ACE as a fallback entry alongside Everyone. The maximal access calculation also combines access masks from every ACE, regardless of whether its SID applies to the current user. This can grant rights belonging to an unrelated principal. Process only ACEs applying to the user, Everyone, or Authenticated Users, and accumulate allowed and denied masks in ACL order. Preserve explicitly requested access bits so they are validated against the resulting maximal mask. When ACCESS_SYSTEM_SECURITY is denied, report STATUS_PRIVILEGE_NOT_HELD instead of the generic STATUS_ACCESS_DENIED. Access to the system ACL requires a security privilege that ksmbd does not grant. For regular files, include FILE_EXECUTE in maximal access when the client requested GENERIC_EXECUTE and the DACL grants the complete file-read set. Keep a direct FILE_EXECUTE request subject to the explicit DACL bit. This matches the POSIX file ACL mapping without broadening specific execute requests. Do not replace rights from an applicable NT ACE with a POSIX ACL entry. The POSIX ACL is only a fallback when no user, Everyone, or Authenticated Users ACE applies; otherwise it can incorrectly broaden the stored DACL. This fixes smb2.maximum_allowed.maximum_allowed.
How do I check if I'm vulnerable to CVE-2026-93282? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Don't wait for an exploit

Scan your website for vulnerabilities like CVE-2026-93282 — free, no signup required.