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Fencer Vulns
high 7.8

CVE-2025-39963 json

io_uring: fix incorrect io_kiocb reference in io_link_skb

published 2025-10-09 13 mo ago modified 2026-10-19 20 d ago also EUVD-2025-33335

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits
0
none known

Summary

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

io_uring: fix incorrect io_kiocb reference in io_link_skb

In io_link_skb function, there is a bug where prev_notif is incorrectly assigned using 'nd' instead of 'prev_nd'. This causes the context validation check to compare the current notification with itself instead of comparing it with the previous notification.

Fix by using the correct prev_nd parameter when obtaining prev_notif.

Patch / fix

  • Linux Linux 6.12.49, 6.16.9, 6.17
  • linux Debian 13 6.12.57-1
  • linux Debian 14 6.16.9-1

debian advisories DEBIAN-CVE-2025-39963

  • kernel-livepatch-SLE16_Update_1 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 3-160000.1.1
  • kernel-livepatch-SLE16_Update_0 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 5-160000.4.3
  • kernel-livepatch-SLE16-RT_Update_1 Linux Micro 6.2 3-160000.1.1
  • kernel-livepatch-SLE16-RT_Update_0 Linux Micro 6.2 4-160000.3.4
  • kernel-rt Linux Micro 6.2 6.12.0-160000.7.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.7.1

suse advisories SUSE-SU-2026:20171-1SUSE-SU-2026:20202-1SUSE-SU-2026:20149-1SUSE-SU-2026:20169-1SUSE-SU-2026:20168-1SUSE-SU-2026:20164-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.7.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-kvmsmall openSUSE Leap 16.0 6.12.0-160000.7.1

opensuse advisories openSUSE-SU-2025:20091-1

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-2025-39963 updated cvss 5.5

kernel: io_uring: fix incorrect io_kiocb reference in io_link_skb

  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    affected: workaround, no fix available “Fix deferred”
  • 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
    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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
24 d ago

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-401 Missing Release of Memory after Effective Lifetime
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.