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Fencer Vulns
medium 5.5

CVE-2025-68823 json

ublk: fix deadlock when reading partition table

published 2026-01-13 9 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-2278

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

ublk: fix deadlock when reading partition table

When one process(such as udev) opens ublk block device (e.g., to read the partition table via bdev_open()), a deadlock[1] can occur:

1. bdev_open() grabs disk->open_mutex 2. The process issues read I/O to ublk backend to read partition table 3. In __ublk_complete_rq(), blk_update_request() or blk_mq_end_request() runs bio->bi_end_io() callbacks 4. If this triggers fput() on file descriptor of ublk block device, the work may be deferred to current task's task work (see fput() implementation) 5. This eventually calls blkdev_release() from the same context 6. blkdev_release() tries to grab disk->open_mutex again 7. Deadlock: same task waiting for a mutex it already holds

The fix is to run blk_update_request() and blk_mq_end_request() with bottom halves disabled. This forces blkdev_release() to run in kernel work-queue context instead of current task work context, and allows ublk server to make forward progress, and avoids the deadlock.

[axboe: rewrite comment in ublk]

Patch / fix

  • Linux Linux 6.1.175, 6.6.124, 6.12.70, 6.18.3, 6.19
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.73-1
  • linux Debian 14 6.18.3-1

debian advisories DEBIAN-CVE-2025-68823

  • linux Ubuntu 24.04 LTS 6.8.0-117.117
  • linux Ubuntu 25.10 6.17.0-22.22
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1055.58
  • linux-aws Ubuntu 25.10 6.17.0-1012.12
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1058.61
  • linux-gcp Ubuntu 25.10 6.17.0-1012.12
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1054.60
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1055.56

ubuntu advisories UBUNTU-CVE-2025-68823

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-68823 updated cvss 5.5

kernel: Linux kernel: Denial of Service in ublk due to deadlock when reading partition table

  • Red Hat Enterprise Linux 10 kernel
    affected: no fix available
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.