Bug 2455337 (CVE-2026-31409)

Summary: CVE-2026-31409 kernel: ksmbd: unset conn->binding on failed binding request
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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A flaw was found in ksmbd, a component of the Linux kernel. This vulnerability occurs when a multichannel Server Message Block (SMB2) session setup request, specifically one with a binding flag, fails. Due to an error in handling this failure, ksmbd incorrectly retains a binding state for the connection. This can lead to all subsequent session lookups falling back to a global sessions table, potentially causing unexpected session management and service disruption.
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Description OSIDB Bzimport 2026-04-06 09:01:37 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ksmbd: unset conn->binding on failed binding request

When a multichannel SMB2_SESSION_SETUP request with
SMB2_SESSION_REQ_FLAG_BINDING fails ksmbd sets conn->binding = true
but never clears it on the error path. This leaves the connection in
a binding state where all subsequent ksmbd_session_lookup_all() calls
fall back to the global sessions table. This fix it by clearing
conn->binding = false in the error path.
Comment 1 Keith Grant 2026-04-06 11:51:05 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026040629-CVE-2026-31409-d22c@gregkh/T