Vulnerability-Lookup

CVE-2026-64262 (GCVE-0-2026-64262)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:49 – Updated: 2026-07-25 08:49

Title

fuse-uring: end fuse_req on io-uring cancel task work

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).

Severity

No CVSS data available.

Assigner

Linux

References

3 references

URL	Tags
https://git.kernel.org/stable/c/bb476ef8e1027a9d5…
https://git.kernel.org/stable/c/4f45f276d5b4412ea…
https://git.kernel.org/stable/c/bea4fe98204b6ce7e…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: c2c9af9a0b13261c36909036057a116f2edb5e1a , < bb476ef8e1027a9d509fbaaf81f5061a07e9e5a7 (git) Affected: c2c9af9a0b13261c36909036057a116f2edb5e1a , < 4f45f276d5b4412eade6f74f2e37f3adba0473ed (git) Affected: c2c9af9a0b13261c36909036057a116f2edb5e1a , < bea4fe98204b6ce7eb8e29f7bf867dd7619b3ddd (git)
Linux	Linux	Affected: 6.14 Unaffected: 0 , < 6.14 (semver) Unaffected: 6.18.39 , ≤ 6.18.* (semver) Unaffected: 7.1.4 , ≤ 7.1.* (semver) Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)

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JSON

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        }
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    "datePublished": "2026-07-25T08:49:12.599Z",
    "dateReserved": "2026-07-19T15:36:31.774Z",
    "dateUpdated": "2026-07-25T08:49:12.599Z",
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    "suse_vex": {
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      "cve": "CVE-2026-64262",
      "id": "CVE-2026-64262",
      "initial_release_date": "2026-07-25T16:47:04Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64262",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64262.json",
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}

GHSA-FXM4-5828-J89M

Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-07-25 12:31

Details

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).

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JSON

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64262"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-25T10:17:06Z",
    "severity": null
  },
  "details": "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": "GHSA-fxm4-5828-j89m",
  "modified": "2026-07-25T12:31:28Z",
  "published": "2026-07-25T12:31:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64262"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4f45f276d5b4412eade6f74f2e37f3adba0473ed"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bb476ef8e1027a9d509fbaaf81f5061a07e9e5a7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bea4fe98204b6ce7eb8e29f7bf867dd7619b3ddd"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

CVE-2026-64262 (GCVE-0-2026-64262)

GHSA-FXM4-5828-J89M

Tags

Sightings

Nomenclature