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.
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.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data.
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
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 |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-11-07T14:08:46.188Z
Reserved: 2026-09-25T10:25:14.405Z
Link: CVE-2026-99275
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-11-07T14:17:02.850
Modified: 2026-11-07T14:17:02.850
Link: CVE-2026-99275
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.