GHSA-H4XP-2GP9-VPWG
Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-17 18:31In the Linux kernel, the following vulnerability has been resolved:
cuse: wait for pending RCU callbacks on module exit
Since commit 053fc4f755ad ("fuse: fix UAF in rcu pathwalks"), fuse_conn_put() frees the fuse_conn through call_rcu() rather than synchronously. For cuse, fc->release is cuse_fc_release(), which lives in the cuse module. If the module is removed before the RCU grace period ends, the callback jumps into freed module memory:
userspace / module unload | RCU softirq
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ close(/dev/cuse) | cuse_channel_release() | fuse_dev_release() | fuse_conn_put(fch->conn) | call_rcu(delayed_release) ------+---> callback queued | rmmod cuse | cuse_exit() | cuse_channel_destroy() | ... | return | | | | rcu_do_batch() | delayed_release() | fc->release() | -> cuse_fc_release() | ^^^ freed text!
The freed module text is unmapped by vfree(), so the jump into the stale callback triggers a page-fault Oops. If the virtual address is subsequently reused, the callback could execute unrelated code (undefined behaviour).
Fix this by calling rcu_barrier() in cuse_exit() so that any pending fuse_conn release callback completes before the module is removed.
{
"affected": [],
"aliases": [
"CVE-2026-90140"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:17:06Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncuse: wait for pending RCU callbacks on module exit\n\nSince commit 053fc4f755ad (\"fuse: fix UAF in rcu pathwalks\"),\nfuse_conn_put() frees the fuse_conn through call_rcu() rather than\nsynchronously. For cuse, fc-\u003erelease is cuse_fc_release(), which\nlives in the cuse module. If the module is removed before the RCU\ngrace period ends, the callback jumps into freed module memory:\n\n userspace / module unload | RCU softirq\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n close(/dev/cuse) |\n cuse_channel_release() |\n fuse_dev_release() |\n fuse_conn_put(fch-\u003econn) |\n call_rcu(delayed_release) ------+---\u003e callback queued\n |\n rmmod cuse |\n cuse_exit() |\n cuse_channel_destroy() |\n ... |\n return |\n |\n \u003cmodule text freed\u003e |\n | rcu_do_batch()\n | delayed_release()\n | fc-\u003erelease()\n | -\u003e cuse_fc_release()\n | ^^^ freed text!\n\nThe freed module text is unmapped by vfree(), so the jump into the\nstale callback triggers a page-fault Oops. If the virtual address\nis subsequently reused, the callback could execute unrelated code\n(undefined behaviour).\n\nFix this by calling rcu_barrier() in cuse_exit() so that any pending\nfuse_conn release callback completes before the module is removed.",
"id": "GHSA-h4xp-2gp9-vpwg",
"modified": "2026-09-17T18:31:52Z",
"published": "2026-09-17T18:31:52Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90140"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/389bd349ddbcf90dbd8a4f2a4ab6e552d53df134"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/45ae914b2f6ea56fc2f1c017fdee4e995bcb4c0e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4deb3edead0c0e172cc7349e8855d741d3c5e162"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7fe415e1cd8fa875be263670c0ab47109818abb6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a1b46aee33d83f14ed62d7fdef1a91d3e0b732a9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ac5c499413385cea3e0220d6050408d50842891d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c40f3f24839f8404325a2099e26c2a04786ae309"
}
],
"schema_version": "1.4.0",
"severity": []
}
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