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CVE-2025-71070

ublk: clean up user copy references on ublk server exit

Description

In the Linux kernel, the following vulnerability has been resolved: ublk: clean up user copy references on ublk server exit If a ublk server process releases a ublk char device file, any requests dispatched to the ublk server but not yet completed will retain a ref value of UBLK_REFCOUNT_INIT. Before commit e63d2228ef83 ("ublk: simplify aborting ublk request"), __ublk_fail_req() would decrement the reference count before completing the failed request. However, that commit optimized __ublk_fail_req() to call __ublk_complete_rq() directly without decrementing the request reference count. The leaked reference count incorrectly allows user copy and zero copy operations on the completed ublk request. It also triggers the WARN_ON_ONCE(refcount_read(&io->ref)) warnings in ublk_queue_reinit() and ublk_deinit_queue(). Commit c5c5eb24ed61 ("ublk: avoid ublk_io_release() called after ublk char dev is closed") already fixed the issue for ublk devices using UBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference count leak also affects UBLK_F_USER_COPY, the other reference-counted data copy mode. Fix the condition in ublk_check_and_reset_active_ref() to include all reference-counted data copy modes. This ensures that any ublk requests still owned by the ublk server when it exits have their reference counts reset to 0.

Timeline

  1. ID reserved

    By Linux

  2. Published

  3. · 7 months later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2025-71070, by who scored it
Scored byCVSSScoreVector
LinuxCNA (assigner)3.1High7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVDNVD · Deferred3.1High7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (exploitation in 30 days)
0.14% · top 96% of all CVEs (9 Nov 2026)
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Affected products

  • Linux · Linux

    • affected e63d2228ef831af36f963b3ab8604160cfff84c1 – < 13456b4f1033d911f8bf3a0a1195656f293ba0f6
    • affected e63d2228ef831af36f963b3ab8604160cfff84c1 – < daa24603d9f0808929514ee62ced30052ca7221c
    • affected e537193fc4a43b48ac51cc6366319e15e32dd540
    • affected 6.14.6 – < 6.15

  • Linux · Linux

    • affected 6.15
    • unaffected < 6.15
    • unaffected 6.18.3 – ≤ 6.18.*
    • unaffected 6.19 – ≤ *

References

2

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .