GHSA-3FC8-28WQ-WQ67
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-10-30 15:33In the Linux kernel, the following vulnerability has been resolved:
smb: client: reject userspace cifs.idmap descriptions
cifs.idmap key descriptions carry authority-bearing fields (owner and group SIDs and uid/gid values in "os:"/"gs:"/"oi:"/"gi:" form) that the cifs.idmap upcall helper treats as kernel-originating inputs. Unlike its sibling cifs.spnego, the cifs.idmap key type has no vet_description hook, so userspace can create keys of this type through request_key(2)/add_key(2) and supply those fields without CIFS origin. A request_key(2) call with a non-NULL callout then drives a root usermodehelper upcall (/sbin/request-key -> cifs.idmap) that consumes the unvetted description in root context.
Only accept cifs.idmap descriptions while CIFS is using its private root_cred to request the key. id_to_sid()/sid_to_id() already run under override_creds(root_cred), so the kernel-originated path is unaffected.
This mirrors commit 3da1fdf4efbc ("smb: client: reject userspace cifs.spnego descriptions"), which applied the same restriction to cifs.spnego.
{
"affected": [],
"aliases": [
"CVE-2026-97564"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:07Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject userspace cifs.idmap descriptions\n\ncifs.idmap key descriptions carry authority-bearing fields (owner and\ngroup SIDs and uid/gid values in \"os:\"/\"gs:\"/\"oi:\"/\"gi:\" form) that the\ncifs.idmap upcall helper treats as kernel-originating inputs. Unlike\nits sibling cifs.spnego, the cifs.idmap key type has no vet_description\nhook, so userspace can create keys of this type through\nrequest_key(2)/add_key(2) and supply those fields without CIFS origin.\nA request_key(2) call with a non-NULL callout then drives a root\nusermodehelper upcall (/sbin/request-key -\u003e cifs.idmap) that consumes\nthe unvetted description in root context.\n\nOnly accept cifs.idmap descriptions while CIFS is using its private\nroot_cred to request the key. id_to_sid()/sid_to_id() already run\nunder override_creds(root_cred), so the kernel-originated path is\nunaffected.\n\nThis mirrors commit 3da1fdf4efbc (\"smb: client: reject userspace\ncifs.spnego descriptions\"), which applied the same restriction to\ncifs.spnego.",
"id": "GHSA-3fc8-28wq-wq67",
"modified": "2026-10-30T15:33:47Z",
"published": "2026-09-25T12:31:24Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97564"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/17c93bcd17755523c21abb22cbf2a41a6eb0caaf"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1d3b24b16a0b013792e8f1e3ed060f0b46f537d1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/856cb3f05b49d23dc1542f78696e20c4ea6dd7de"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/91da70a2e5c6f54e1316d51e0e6911e78ef5e09a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/96751028c0d4dec785709ea3eb0ab38a4f2ded96"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d9d7eeb0cea5b55b82888f443622fd8d4ee064f3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e5964064e3fbe6325893408faff08ca33de0e2c3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f29c1ec0e7d8c887a91df3f93bb4617c0ac95c6a"
}
],
"schema_version": "1.4.0",
"severity": []
}
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