EUVD-2026-39222
GHSA-hxmm-jmj9-253j
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
ksmbd is network-bound and the oops is explicitly 'remotely triggerable,' warranting AV:N; AC:H reflects race-condition timing dependency; PR:L for required authenticated SMB session.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix NULL-deref of opinfo->conn in oplock/lease break notifiers
smb2_oplock_break_noti() and smb2_lease_break_noti() read opinfo->conn into a local with neither READ_ONCE() nor a NULL check. Both run from oplock_break() after opinfo_get_list() has dropped ci->m_lock, so a concurrent SMB2 LOGOFF (session_fd_check()) can set op->conn = NULL under ci->m_lock within that window. ksmbd_conn_r_count_inc(conn) then writes through NULL at offset 0xc4 -- a remotely triggerable oops.
Guard both reads the way compare_guid_key() already does: read opinfo->conn with READ_ONCE() and return early if it is NULL, before allocating the work struct so nothing leaks. A NULL conn means the client is gone and the break is moot, so return 0; oplock_break() treats that as success and runs the normal teardown.
AnalysisAI
NULL pointer dereference in the ksmbd (in-kernel SMB server) subsystem of the Linux kernel causes a remotely triggerable kernel oops, resulting in denial of service. The race condition in smb2_oplock_break_noti() and smb2_lease_break_noti() allows an authenticated SMB client to crash the kernel by racing an SMB2 LOGOFF against an oplock/lease break notification - setting opinfo->conn to NULL in the window after ci->m_lock is dropped, then dereferencing it in ksmbd_conn_r_count_inc(). …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | ksmbd must be running as the active SMB server (kernel module loaded, service configured and listening - this is a non-default state on all major Linux distributions and requires explicit administrator configuration). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The official CVSS 3.1 score of 5.5 (Medium, AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) likely understates the attack vector: the description explicitly calls this 'a remotely triggerable oops,' and ksmbd is a network-bound SMB server - AV:N with AC:H (race condition) and PR:L (authenticated SMB session) is arguably more representative. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a valid SMB account on a ksmbd-serving Linux host opens a file to acquire an oplock, then races an SMB2 LOGOFF request against the server's oplock break notification for that file. In the window after oplock_break() drops ci->m_lock but before the notifier checks opinfo->conn, the LOGOFF handler zeros conn, causing the notifier to call ksmbd_conn_r_count_inc(NULL) and write through a NULL pointer at kernel offset 0xc4, producing a kernel oops and system crash. … |
| Remediation | Patch to Linux kernel 6.6.143, 6.12.94, 7.0.13, or 7.1 stable release - whichever corresponds to the deployed stable branch. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-476 – NULL Pointer Dereference
View allSame technique Denial Of Service
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External POC / Exploit Code
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