EUVD Vulnerability Catalog
EUVD-2026-76248
Severity: CRITICAL
Base Score: 9.8
CVSS Version: 3.1
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix use-after-free in oplock break notification
smb2_oplock_break_noti() reads opinfo->conn without any lock and
dereferences it after two allocations which may sleep. When the
durable handle owning the oplock is disconnected, session_fd_check()
clears opinfo->conn and drops its conn reference under ci->m_lock, and
the last ksmbd_conn_put() frees the connection. A break triggered by
another connection that races with the teardown can then resurrect the
freed connection: ksmbd_conn_get() is a plain atomic_inc, and the
queued break work later dereferences the stale conn via
ksmbd_conn_write(), a use-after-free reachable by any authenticated
client holding a durable batch oplock.
Thread the caller's inode into the notification path instead of taking
a new reference on it. Every caller of oplock_break() already holds a
live ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference,
in the parent lease break paths) on the inode that owns the break
target's oplock list, so ci cannot be freed during the call, and its
lock can be taken without dereferencing opinfo->o_fp, which a
concurrent close may free. Select and pin the connection under
ci->m_lock, the same lock session_fd_check() and
ksmbd_reopen_durable_fd() use to update opinfo->conn, so a concurrent
detach either loses the race to the clear or keeps the connection
alive until the notification work releases it. Transfer the reference
to the work item and release it on allocation failures.
CVSS Vector Analysis
Below is the complete, human-readable breakdown of the CVSS metric string: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
▪
Attack Vector (AV): Network
▪
Attack Complexity (AC): Low
▪
Privileges Required (PR): None
▪
User Interaction (UI): None
▪
Scope (S): Unchanged
▪
Confidentiality Impact (C): High
▪
Integrity Impact (I): High
▪
Availability Impact (A): High
Affected Vendors & Systems
Vendor
Linux
References & Advisory Links
- https://git.kernel.org/stable/c/892f643b141aee3f7aa7c0fc61ddcb55c59f1996
- https://git.kernel.org/stable/c/5de0527f782430b1109a447646e32033ad018a6a
- https://git.kernel.org/stable/c/c8279ae8df68cce9cd3b785e85f7a86c80a46e78
- https://git.kernel.org/stable/c/8cc98db4fc590e6c7d9db6529320982ee16c5d1d
- https://git.kernel.org/stable/c/0e753899627b5e28a9fea8bca98262a6f65a2452
Metadata Profile
Database Authority
European Union Agency for Cybersecurity (ENISA) EUVD
Assigner
Linux
EPSS Probability
0.65
Known Aliases
GHSA-4r76-cqqc-v36j
CVE-2026-80926
Published On
2026-09-11
Last Updated
2026-10-03