In the Linux kernel, the following vulnerability has been resolved:
ksmbd: reject repeated SMB2 NEGOTIATE requests
Unauthenticated client can send multiple successful SMB2 NEGOTIATE
requests on one connection before SESSION_SETUP. While the connection is
in KSMBD_SESS_NEED_SETUP, smb2_handle_negotiate() accepts another
SMB3.1.1 NEGOTIATE and overwrites conn->preauth_info with a new allocation.
Only the final allocation is freed when the connection is released, leaking
one object for every additional successful request.
A repeated SMB2 NEGOTIATE after a dialect has been selected is a protocol
violation. MS-SMB2 section 3.3.5.4 requires the server to disconnect
without replying in this case. Set the connection exiting when rejecting
the request, in addition to suppressing the response.
Reject SMB2 NEGOTIATE unless the connection is new or is waiting for the
SMB2 NEGOTIATE that follows an SMB1 multi-protocol negotiate. Serialize
both SMB1 and SMB2 negotiation paths under conn->srv_mutex, since they
update connection-wide dialect and negotiation state.
Move the locking contract to ksmbd_smb_negotiate_common(), where the state
and dialect are selected, and add ksmbd_conn_new() for consistent state
access.
ksmbd: reject repeated SMB2 NEGOTIATE requests
Unauthenticated client can send multiple successful SMB2 NEGOTIATE
requests on one connection before SESSION_SETUP. While the connection is
in KSMBD_SESS_NEED_SETUP, smb2_handle_negotiate() accepts another
SMB3.1.1 NEGOTIATE and overwrites conn->preauth_info with a new allocation.
Only the final allocation is freed when the connection is released, leaking
one object for every additional successful request.
A repeated SMB2 NEGOTIATE after a dialect has been selected is a protocol
violation. MS-SMB2 section 3.3.5.4 requires the server to disconnect
without replying in this case. Set the connection exiting when rejecting
the request, in addition to suppressing the response.
Reject SMB2 NEGOTIATE unless the connection is new or is waiting for the
SMB2 NEGOTIATE that follows an SMB1 multi-protocol negotiate. Serialize
both SMB1 and SMB2 negotiation paths under conn->srv_mutex, since they
update connection-wide dialect and negotiation state.
Move the locking contract to ksmbd_smb_negotiate_common(), where the state
and dialect are selected, and add ksmbd_conn_new() for consistent state
access.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Sat, 15 Aug 2026 12:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: ksmbd: reject repeated SMB2 NEGOTIATE requests Unauthenticated client can send multiple successful SMB2 NEGOTIATE requests on one connection before SESSION_SETUP. While the connection is in KSMBD_SESS_NEED_SETUP, smb2_handle_negotiate() accepts another SMB3.1.1 NEGOTIATE and overwrites conn->preauth_info with a new allocation. Only the final allocation is freed when the connection is released, leaking one object for every additional successful request. A repeated SMB2 NEGOTIATE after a dialect has been selected is a protocol violation. MS-SMB2 section 3.3.5.4 requires the server to disconnect without replying in this case. Set the connection exiting when rejecting the request, in addition to suppressing the response. Reject SMB2 NEGOTIATE unless the connection is new or is waiting for the SMB2 NEGOTIATE that follows an SMB1 multi-protocol negotiate. Serialize both SMB1 and SMB2 negotiation paths under conn->srv_mutex, since they update connection-wide dialect and negotiation state. Move the locking contract to ksmbd_smb_negotiate_common(), where the state and dialect are selected, and add ksmbd_conn_new() for consistent state access. | |
| Title | ksmbd: reject repeated SMB2 NEGOTIATE requests | |
| 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: 2026-08-15T12:27:22.609Z
Reserved: 2026-08-15T05:44:03.906Z
Link: CVE-2026-74494
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-15T13:17:54.353
Modified: 2026-08-15T13:17:54.353
Link: CVE-2026-74494
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.