FKIE_CVE-2026-64262
Vulnerability from fkie_nvd - Published: 2026-07-25 10:17 - Updated: 2026-07-30 15:00
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
fuse-uring: end fuse_req on io-uring cancel task work
When io_uring delivers task work with tw.cancel set (PF_EXITING,
PF_KTHREAD fallback, or percpu_ref_is_dying on the ring context),
fuse_uring_send_in_task() takes the cancel branch, assigns
-ECANCELED, and falls through to fuse_uring_send(). That path only
flips the entry to FRRS_USERSPACE and completes the io_uring cmd;
it never discharges the ring entry's owning reference to the
fuse_req that fuse_uring_add_req_to_ring_ent() handed it at
dispatch time.
fuse_uring_send_in_task()
tw.cancel == true
err = -ECANCELED
fuse_uring_send(ent, cmd, err, issue_flags)
ent->state = FRRS_USERSPACE
list_move(&ent->list, &queue->ent_in_userspace)
ent->cmd = NULL
io_uring_cmd_done(-ECANCELED)
/* ent->fuse_req still set, req still hashed */
The fuse_req stays linked on fpq->processing[hash] and
fuse_request_end() is never invoked. The originating syscall
thread blocks in D-state in request_wait_answer() until
fuse_abort_conn() runs, which can be the entire connection
lifetime. For FR_BACKGROUND requests fc->num_background is never
decremented either, so repeated cancels inflate the counter until
max_background is hit and all later background ops stall. tw.cancel does
not imply a connection abort (e.g. a single io_uring worker thread exits
while the fuse connection stays up), so this cannot be left for
fuse_abort_conn() to clean up.
Ending the req but still routing the entry through fuse_uring_send()
is not enough: that leaves a req-less entry on ent_in_userspace, and
ent_list_request_expired() dereferences ent->fuse_req unconditionally
on the head of that list, which would then NULL-deref.
Fix the cancel branch to release the entry directly. Remove it from the
queue, complete the io_uring cmd, end the fuse_req, free the entry, and
drop its queue_refs (waking the teardown waiter if it was the last).
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/fuse/dev_uring.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "bb476ef8e1027a9d509fbaaf81f5061a07e9e5a7",
"status": "affected",
"version": "c2c9af9a0b13261c36909036057a116f2edb5e1a",
"versionType": "git"
},
{
"lessThan": "4f45f276d5b4412eade6f74f2e37f3adba0473ed",
"status": "affected",
"version": "c2c9af9a0b13261c36909036057a116f2edb5e1a",
"versionType": "git"
},
{
"lessThan": "bea4fe98204b6ce7eb8e29f7bf867dd7619b3ddd",
"status": "affected",
"version": "c2c9af9a0b13261c36909036057a116f2edb5e1a",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/fuse/dev_uring.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.14"
},
{
"lessThan": "6.14",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.39",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfuse-uring: end fuse_req on io-uring cancel task work\n\nWhen io_uring delivers task work with tw.cancel set (PF_EXITING,\nPF_KTHREAD fallback, or percpu_ref_is_dying on the ring context),\nfuse_uring_send_in_task() takes the cancel branch, assigns\n-ECANCELED, and falls through to fuse_uring_send(). That path only\nflips the entry to FRRS_USERSPACE and completes the io_uring cmd;\nit never discharges the ring entry\u0027s owning reference to the\nfuse_req that fuse_uring_add_req_to_ring_ent() handed it at\ndispatch time.\n\n fuse_uring_send_in_task()\n tw.cancel == true\n err = -ECANCELED\n fuse_uring_send(ent, cmd, err, issue_flags)\n ent-\u003estate = FRRS_USERSPACE\n list_move(\u0026ent-\u003elist, \u0026queue-\u003eent_in_userspace)\n ent-\u003ecmd = NULL\n io_uring_cmd_done(-ECANCELED)\n /* ent-\u003efuse_req still set, req still hashed */\n\nThe fuse_req stays linked on fpq-\u003eprocessing[hash] and\nfuse_request_end() is never invoked. The originating syscall\nthread blocks in D-state in request_wait_answer() until\nfuse_abort_conn() runs, which can be the entire connection\nlifetime. For FR_BACKGROUND requests fc-\u003enum_background is never\ndecremented either, so repeated cancels inflate the counter until\nmax_background is hit and all later background ops stall. tw.cancel does\nnot imply a connection abort (e.g. a single io_uring worker thread exits\nwhile the fuse connection stays up), so this cannot be left for\nfuse_abort_conn() to clean up.\n\nEnding the req but still routing the entry through fuse_uring_send()\nis not enough: that leaves a req-less entry on ent_in_userspace, and\nent_list_request_expired() dereferences ent-\u003efuse_req unconditionally\non the head of that list, which would then NULL-deref.\n\nFix the cancel branch to release the entry directly. Remove it from the\nqueue, complete the io_uring cmd, end the fuse_req, free the entry, and\ndrop its queue_refs (waking the teardown waiter if it was the last)."
}
],
"id": "CVE-2026-64262",
"lastModified": "2026-07-30T15:00:27.343",
"metrics": {},
"published": "2026-07-25T10:17:06.350",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/4f45f276d5b4412eade6f74f2e37f3adba0473ed"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/bb476ef8e1027a9d509fbaaf81f5061a07e9e5a7"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/bea4fe98204b6ce7eb8e29f7bf867dd7619b3ddd"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Awaiting Analysis"
}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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