CVE-2026-64017 (GCVE-0-2026-64017)

Vulnerability from cvelistv5 – Published: 2026-07-19 15:39 – Updated: 2026-08-19 16:28
VLAI
Title
blk-mq: pop cached request if it is usable
Summary
In the Linux kernel, the following vulnerability has been resolved: blk-mq: pop cached request if it is usable When submitting a bio to blk-mq, if the task should sleep after peeking a cached request, but before it pops it, the plug flushes and calls blk_mq_free_plug_rqs, freeing the cached_rqs. This creates a use-after-free bug. Fix this by popping the cached request before any possible blocking calls if it is suitable for use. Popping this request first holds a queue reference, so avoid any serialization races with queue freezes and can safely proceed with dispatching that request to the driver. This potentially increases a timing window from when a driver wants to freeze its queue to when requests stop being dispatched. That scenario is off the fast path though, and drivers need to appropriately handle requests during a freeze request anyway. The downside is the popped element needs to be individually freed when we performed a bio plug merge. The cached request would have had to be freed later anyway, but this patch does it inline with building the plug list instead of after flushing it.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b0077e269f6c152e807fdac90b58caf012cdbaab , < 23d8ea1e303b5f32d883757a4a707e791dbc9808 (git)
Affected: b0077e269f6c152e807fdac90b58caf012cdbaab , < 97e2d08de282ef76f84ab4ccd00f1acb3f5f999e (git)
Affected: b0077e269f6c152e807fdac90b58caf012cdbaab , < 388468f7e7d1eab092cf2a39fdfb502e52019ec6 (git)
Affected: b0077e269f6c152e807fdac90b58caf012cdbaab , < dc278e9bf2b9513a763353e6b9cc21e0f532954e (git)
Affected: b5c8e0ff76d10f6bf70a7237678f27c20cf59bc9 (git)
Affected: e9c309ded295b7f8849097d71ae231456ca79f78 (git)
Affected: b80056bd75a16e4550873ecefe12bc8fd190b1cf (git)
Affected: 33cf52b6e53a6aa55883aa7fb9ceffceff8488a6 (git)
Affected: 8b6075046470c8756242dfe3fd058813636f69a3 (git)
Affected: 6.1.72 , < 6.2 (semver)
Affected: 6.5.13 , < 6.6 (semver)
Affected: 6.6.3 , < 6.7 (semver)
Affected: 6.1.75 , < 6.2 (semver)
Affected: 6.6.14 , < 6.7 (semver)
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Linux Linux Affected: 6.7
Unaffected: 0 , < 6.7 (semver)
Unaffected: 6.12.104 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.0.11 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblk-mq: pop cached request if it is usable\n\nWhen submitting a bio to blk-mq, if the task should sleep after peeking\na cached request, but before it pops it, the plug flushes and calls\nblk_mq_free_plug_rqs, freeing the cached_rqs. This creates a\nuse-after-free bug. Fix this by popping the cached request before any\npossible blocking calls if it is suitable for use.\n\nPopping this request first holds a queue reference, so avoid any\nserialization races with queue freezes and can safely proceed with\ndispatching that request to the driver. This potentially increases a\ntiming window from when a driver wants to freeze its queue to when\nrequests stop being dispatched. That scenario is off the fast path\nthough, and drivers need to appropriately handle requests during a\nfreeze request anyway.\n\nThe downside is the popped element needs to be individually freed when\nwe performed a bio plug merge. The cached request would have had to be\nfreed later anyway, but this patch does it inline with building the plug\nlist instead of after flushing it."
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              "value": "AV:L - The bug is in `blk_mq_submit_bio()`, reached from local block I/O submission (`submit_bio` via read/write, filesystem I/O, or io_uring). Reliable exploitation requires a `blk_plug` with populated `cached_rqs`, which occurs when io_uring submits batches of 3+ plugged read/write operations (`blk_start_plug_nr_ios`); remote-only paths like nfsd/ksmbd/nvmet typically use `blk_start_plug()` with `nr_ios=1` and do not populate the cached-request list needed to hit the peek-without-pop window.\nAC:L - An attacker controls both sides of the race by batching io_uring I/O and inducing a sleep between peek and pop (e.g., memory pressure during bio split/allocation, or `bio_integrity_prep()` blocking on PI-capable enterprise/cloud NVMe). Plug flush on any schedule is deterministic kernel behavior, not an uncontrollable environmental condition.\nPR:L - Triggering requires only an unprivileged local process able to perform block-backed I/O (normal file read/write or io_uring readv/writev to accessible storage); no root, `CAP_SYS_ADMIN`, or special kernel capabilities are needed beyond standard filesystem/device access available to any local user.\nUI:N - Exploitation is driven entirely by the attacker\u0027s own I/O submissions through io_uring or direct block I/O; no action by another user or administrator is required.\nS:U - Impact is confined to kernel memory via a block-layer use-after-free on `struct request`; this is standard kernel privilege escalation territory and does not cross a VM, IOMMU, or sandbox security boundary.\nC:H - This is a use-after-free of a `struct request` object; the attacker can influence post-free heap contents and dereference freed fields (`rq-\u003eq`, `rq-\u003emq_hctx`, `rq-\u003ebio`), enabling arbitrary kernel memory read primitives.\nI:H - UAF on `struct request` permits controlled writes through subsequent use of the dangling object (`rq-\u003ecmd_flags`, `queuelist`, bio attachment in `blk_mq_bio_to_request`), enabling heap corruption and potential arbitrary code execution in kernel context.\nA:H - The freed request is dereferenced during `blk_mq_use_cached_rq()` and subsequent request setup, causing kernel oops/panic; even without full exploitation, UAF reliably threatens system availability."
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This potentially increases a\\ntiming window from when a driver wants to freeze its queue to when\\nrequests stop being dispatched. That scenario is off the fast path\\nthough, and drivers need to appropriately handle requests during a\\nfreeze request anyway.\\n\\nThe downside is the popped element needs to be individually freed when\\nwe performed a bio plug merge. The cached request would have had to be\\nfreed later anyway, but this patch does it inline with building the plug\\nlist instead of after flushing it.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"block/blk-mq.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"b0077e269f6c152e807fdac90b58caf012cdbaab\",\"lessThan\":\"23d8ea1e303b5f32d883757a4a707e791dbc9808\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b0077e269f6c152e807fdac90b58caf012cdbaab\",\"lessThan\":\"97e2d08de282ef76f84ab4ccd00f1acb3f5f999e\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b0077e269f6c152e807fdac90b58caf012cdbaab\",\"lessThan\":\"388468f7e7d1eab092cf2a39fdfb502e52019ec6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b0077e269f6c152e807fdac90b58caf012cdbaab\",\"lessThan\":\"dc278e9bf2b9513a763353e6b9cc21e0f532954e\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b5c8e0ff76d10f6bf70a7237678f27c20cf59bc9\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e9c309ded295b7f8849097d71ae231456ca79f78\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b80056bd75a16e4550873ecefe12bc8fd190b1cf\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"33cf52b6e53a6aa55883aa7fb9ceffceff8488a6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"8b6075046470c8756242dfe3fd058813636f69a3\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6.1.72\",\"lessThan\":\"6.2\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.5.13\",\"lessThan\":\"6.6\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.6.3\",\"lessThan\":\"6.7\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.1.75\",\"lessThan\":\"6.2\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.6.14\",\"lessThan\":\"6.7\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"block/blk-mq.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.7\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.7\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.104\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.45\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.11\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/23d8ea1e303b5f32d883757a4a707e791dbc9808\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/388468f7e7d1eab092cf2a39fdfb502e52019ec6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/97e2d08de282ef76f84ab4ccd00f1acb3f5f999e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/dc278e9bf2b9513a763353e6b9cc21e0f532954e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
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      "current_release_date": "2026-08-20T08:03:17+00:00",
      "cve": "CVE-2026-64017",
      "id": "CVE-2026-64017",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:fixed": "612",
      "product_status:known_affected": "22",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: blk-mq: pop cached request if it is usable",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64017.json",
      "version": "3"
    },
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      "current_release_date": "2026-08-06T01:10:18Z",
      "cve": "CVE-2026-64017",
      "id": "CVE-2026-64017",
      "initial_release_date": "2026-07-21T13:01:28Z",
      "product_status:known_affected": "177",
      "product_status:known_not_affected": "119",
      "product_status:recommended": "41",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64017",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64017.json",
      "version": "3"
    }
  }
}



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