GHSA-4R76-CQQC-V36J
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32In 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.
{
"affected": [],
"aliases": [
"CVE-2026-80926"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:18:56Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in oplock break notification\n\nsmb2_oplock_break_noti() reads opinfo-\u003econn without any lock and\ndereferences it after two allocations which may sleep. When the\ndurable handle owning the oplock is disconnected, session_fd_check()\nclears opinfo-\u003econn and drops its conn reference under ci-\u003em_lock, and\nthe last ksmbd_conn_put() frees the connection. A break triggered by\nanother connection that races with the teardown can then resurrect the\nfreed connection: ksmbd_conn_get() is a plain atomic_inc, and the\nqueued break work later dereferences the stale conn via\nksmbd_conn_write(), a use-after-free reachable by any authenticated\nclient holding a durable batch oplock.\n\nThread the caller\u0027s inode into the notification path instead of taking\na new reference on it. Every caller of oplock_break() already holds a\nlive ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference,\nin the parent lease break paths) on the inode that owns the break\ntarget\u0027s oplock list, so ci cannot be freed during the call, and its\nlock can be taken without dereferencing opinfo-\u003eo_fp, which a\nconcurrent close may free. Select and pin the connection under\nci-\u003em_lock, the same lock session_fd_check() and\nksmbd_reopen_durable_fd() use to update opinfo-\u003econn, so a concurrent\ndetach either loses the race to the clear or keeps the connection\nalive until the notification work releases it. Transfer the reference\nto the work item and release it on allocation failures.",
"id": "GHSA-4r76-cqqc-v36j",
"modified": "2026-09-13T09:32:08Z",
"published": "2026-09-11T21:31:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80926"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0e753899627b5e28a9fea8bca98262a6f65a2452"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8cc98db4fc590e6c7d9db6529320982ee16c5d1d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c8279ae8df68cce9cd3b785e85f7a86c80a46e78"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
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- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.