ksmbd: reject repeated SMB2 NEGOTIATE requests

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74494
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 13:17:54 UTC
Updated2026-08-15 13:17:54 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 a60b5da05e318d9a364dbac38c347c7f24e625e7 git Not specified
CNA Linux Linux affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 7e02cb30e8a1f5fc78cb10b220b06020e36d0bbe git Not specified
CNA Linux Linux affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 cb469993b3a61a72653770856d37af616d72d05f git Not specified
CNA Linux Linux affected 5.15 Not specified
CNA Linux Linux unaffected 5.15 semver Not specified
CNA Linux Linux unaffected 6.18.44 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.8 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc6 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/cb469993b3a61a72653770856d37af616d72d05f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a60b5da05e318d9a364dbac38c347c7f24e625e7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7e02cb30e8a1f5fc78cb10b220b06020e36d0bbe 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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