Bug 2532089 (CVE-2026-89631) - CVE-2026-89631 kernel: smb: client: reject a tree connect response whose byte count is too small
Summary: CVE-2026-89631 kernel: smb: client: reject a tree connect response whose byte...
Keywords:
Status: NEW
Alias: CVE-2026-89631
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-11 20:28 UTC by OSIDB Bzimport
Modified: 2026-10-20 03:52 UTC (History)
17 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2026:85321 0 None None None 2026-10-19 21:47:20 UTC
Red Hat Product Errata RHSA-2026:85773 0 None None None 2026-10-20 03:52:00 UTC
Red Hat Product Errata RHSA-2026:85774 0 None None None 2026-10-20 03:42:45 UTC

Description OSIDB Bzimport 2026-09-11 20:28:31 UTC
In the Linux kernel, the following vulnerability has been resolved:

smb: client: reject a tree connect response whose byte count is too small

CIFSTCon() bounds its strnlen() over the byte area with the server's
ByteCount minus two, which for ByteCount 0 or 1 goes negative as an int
and converts to a huge size_t.  The later subtraction wraps the __u16
bytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of
up to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the
slab object, and the bytes reach userspace through tcon->nativeFileSystem
in /proc/fs/cifs/DebugData.

Reject a byte area too small for what the parser consumes.  Two bytes is
the least it can consume, and no conformant response carries fewer.  The
new trace point is the 129th smb_eio_trace entry, which __mode(byte)
cannot represent, so the attribute goes with it.

Comment 3 Jon Orris 2026-10-19 21:47:18 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:85321 https://access.redhat.com/errata/RHSA-2026:85321

Comment 4 Jon Orris 2026-10-20 03:42:43 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:85774 https://access.redhat.com/errata/RHSA-2026:85774

Comment 5 Jon Orris 2026-10-20 03:51:59 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:85773 https://access.redhat.com/errata/RHSA-2026:85773


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