GHSA-24C9-H3QQ-J27F
Vulnerability from github – Published: 2026-05-01 15:30 – Updated: 2026-05-17 18:30In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger
When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list.
Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did:
spin_lock(&fp->conn->llist_lock);
This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect().
The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out.
To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths: - Safely skip clist deletion when list is empty and fp->conn is NULL. - Remove the lock from the old connection's lock_list in session_fd_check() - Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().
{
"affected": [],
"aliases": [
"CVE-2026-31718"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-01T14:16:21Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger\n\nWhen a durable file handle survives session disconnect (TCP close without\nSMB2_LOGOFF), session_fd_check() sets fp-\u003econn = NULL to preserve the\nhandle for later reconnection. However, it did not clean up the byte-range\nlocks on fp-\u003elock_list.\n\nLater, when the durable scavenger thread times out and calls\n__ksmbd_close_fd(NULL, fp), the lock cleanup loop did:\n\n spin_lock(\u0026fp-\u003econn-\u003ellist_lock);\n\nThis caused a slab use-after-free because fp-\u003econn was NULL and the\noriginal connection object had already been freed by\nksmbd_tcp_disconnect().\n\nThe root cause is asymmetric cleanup: lock entries (smb_lock-\u003eclist) were\nleft dangling on the freed conn-\u003elock_list while fp-\u003econn was nulled out.\n\nTo fix this issue properly, we need to handle the lifetime of\nsmb_lock-\u003eclist across three paths:\n - Safely skip clist deletion when list is empty and fp-\u003econn is NULL.\n - Remove the lock from the old connection\u0027s lock_list in\n session_fd_check()\n - Re-add the lock to the new connection\u0027s lock_list in\n ksmbd_reopen_durable_fd().",
"id": "GHSA-24c9-h3qq-j27f",
"modified": "2026-05-17T18:30:27Z",
"published": "2026-05-01T15:30:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31718"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0000a7780e0e446a28a273572f6ea8f7f582f694"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/235e32320a470fcd3998fb3774f2290a0eb302a1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3d6682726c2d3a46d31dae88b8166786b09b03ad"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e33c65f011980b4ad4abfd93585ec2079856368f"
}
],
"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.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- 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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.