Description
In the Linux kernel, the following vulnerability has been resolved:

smb: client: reject short SESSION_SETUP responses

smb2_check_message() accepts frames shorter than struct smb2_pdu when
the SMB2 status is non-zero, before the minimum-PDU check added by
b4694f269e66d. A 64-byte STATUS_MORE_PROCESSING_REQUIRED SESSION_SETUP
response is therefore accepted even though it cannot contain the
SecurityBufferOffset and SecurityBufferLength fields.

The parser then reads those fields from stale bytes left in the reused
receive buffer by an earlier frame. With a long stale
SecurityBufferLength, decode_ntlmssp_challenge() copies up to about
64 KB from beyond the receive object and sends the data back to the
server in the NTLMv2 AUTHENTICATE target info.

Reject short MPR SESSION_SETUP responses before the short-error path,
and validate SecurityBufferOffset + SecurityBufferLength against the
received response length before decoding the challenge.

The ordering bypass is not new: the short-error early return predates
b4694f269e66d, and the unvalidated SecurityBufferLength read predates
the 2016 raw NTLMSSP split in 166cea4dc3a4, so all supported stable
trees are affected. Reproduced on 6.6.87.2; the path is unchanged on
mainline.
Published: 2026-11-07
Score: n/a
EPSS: n/a
KEV: No
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Remediation

No vendor fix or workaround currently provided.

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History

Sat, 07 Nov 2026 16:30:00 +0000

Type Values Removed Values Added
First Time appeared Linux linux
Vendors & Products Linux linux

Sat, 07 Nov 2026 16:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125

Sat, 07 Nov 2026 14:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: smb: client: reject short SESSION_SETUP responses smb2_check_message() accepts frames shorter than struct smb2_pdu when the SMB2 status is non-zero, before the minimum-PDU check added by b4694f269e66d. A 64-byte STATUS_MORE_PROCESSING_REQUIRED SESSION_SETUP response is therefore accepted even though it cannot contain the SecurityBufferOffset and SecurityBufferLength fields. The parser then reads those fields from stale bytes left in the reused receive buffer by an earlier frame. With a long stale SecurityBufferLength, decode_ntlmssp_challenge() copies up to about 64 KB from beyond the receive object and sends the data back to the server in the NTLMv2 AUTHENTICATE target info. Reject short MPR SESSION_SETUP responses before the short-error path, and validate SecurityBufferOffset + SecurityBufferLength against the received response length before decoding the challenge. The ordering bypass is not new: the short-error early return predates b4694f269e66d, and the unvalidated SecurityBufferLength read predates the 2016 raw NTLMSSP split in 166cea4dc3a4, so all supported stable trees are affected. Reproduced on 6.6.87.2; the path is unchanged on mainline.
Title smb: client: reject short SESSION_SETUP responses
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-11-07T14:08:46.188Z

Reserved: 2026-09-25T10:25:14.405Z

Link: CVE-2026-99275

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-07T14:17:02.850

Modified: 2026-11-07T14:17:02.850

Link: CVE-2026-99275

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-11-07T16:15:14Z

Weaknesses