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Fencer Vulns
high 7.8

CVE-2025-21926 json

net: gso: fix ownership in __udp_gso_segment

published 2025-04-01 19 mo ago modified 2026-10-15 25 d ago also EUVD-2025-9395

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 15%
public exploits
0
none known

Summary

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

net: gso: fix ownership in __udp_gso_segment

In __udp_gso_segment the skb destructor is removed before segmenting the skb but the socket reference is kept as-is. This is an issue if the original skb is later orphaned as we can hit the following bug:

kernel BUG at ./include/linux/skbuff.h:3312! (skb_orphan) RIP: 0010:ip_rcv_core+0x8b2/0xca0 Call Trace: ip_rcv+0xab/0x6e0 __netif_receive_skb_one_core+0x168/0x1b0 process_backlog+0x384/0x1100 __napi_poll.constprop.0+0xa1/0x370 net_rx_action+0x925/0xe50

The above can happen following a sequence of events when using OpenVSwitch, when an OVS_ACTION_ATTR_USERSPACE action precedes an OVS_ACTION_ATTR_OUTPUT action:

1. OVS_ACTION_ATTR_USERSPACE is handled (in do_execute_actions): the skb goes through queue_gso_packets and then __udp_gso_segment, where its destructor is removed. 2. The segments' data are copied and sent to userspace. 3. OVS_ACTION_ATTR_OUTPUT is handled (in do_execute_actions) and the same original skb is sent to its path. 4. If it later hits skb_orphan, we hit the bug.

Fix this by also removing the reference to the socket in __udp_gso_segment.

Patch / fix

  • Linux Linux 5.4.291, 5.10.235, 5.15.179, 6.1.131, 6.6.83, 6.12.19, 6.13.7, 6.14
  • linux Debian 12 6.1.133-1
  • linux Debian 14, Debian 13 6.12.19-1

debian advisories DEBIAN-CVE-2025-21926

  • linux Ubuntu 20.04 LTS 5.4.0-216.236
  • linux Ubuntu 22.04 LTS 5.15.0-140.150
  • linux Ubuntu 24.04 LTS 6.8.0-84.84
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1146.156
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1084.91
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1039.41
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1149.158
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1083.92

ubuntu advisories UBUNTU-CVE-2025-21926

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

  • kernel RHEL 10.0 6.12.0-55.16.1.el10_0
  • rv RHEL 10.0 6.12.0-55.16.1.el10_0
  • perf RHEL 10.0 6.12.0-55.16.1.el10_0
  • rtla RHEL 10.0 6.12.0-55.16.1.el10_0
  • libperf RHEL 10.0 6.12.0-55.16.1.el10_0
  • kernel-rt RHEL 10.0 6.12.0-55.16.1.el10_0
  • kernel-64k RHEL 10.0 6.12.0-55.16.1.el10_0
  • kernel-core RHEL 10.0 6.12.0-55.16.1.el10_0

red hat advisories RHSA-2025:8669RHSA-2025:8643

  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-syms-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-source-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1
  • kernel-syms-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1
  • kernel-rt_debug Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1
  • kernel-source-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1
  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.3.1

suse advisories SUSE-SU-2025:01967-1SUSE-SU-2025:01964-1SUSE-SU-2025:01951-1SUSE-SU-2025:01919-1SUSE-SU-2025:01707-1SUSE-SU-2025:20344-1

  • kernel AlmaLinux 9 5.14.0-570.21.1.el9_6
  • rv AlmaLinux 9 5.14.0-570.21.1.el9_6
  • perf AlmaLinux 9 5.14.0-570.21.1.el9_6
  • rtla AlmaLinux 9 5.14.0-570.21.1.el9_6
  • libperf AlmaLinux 9 5.14.0-570.21.1.el9_6
  • kernel-rt AlmaLinux 9 5.14.0-570.21.1.el9_6
  • kernel-64k AlmaLinux 9 5.14.0-570.21.1.el9_6
  • kernel-core AlmaLinux 9 5.14.0-570.21.1.el9_6

almalinux advisories ALSA-2025:8643

  • kernel Rocky Linux 9 5.14.0-570.21.1.el9_6
  • kernel Rocky Linux 10 6.12.0-55.16.1.el10_0

rocky linux advisories RLSA-2025:8643RLSA-2025:8669

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-2025-21926 updated cvss 7.0

kernel: net: gso: fix ownership in __udp_gso_segment

  • 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
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-570.21.1.el9_6, perf 5.14.0-570.21.1.el9_6, rtla 5.14.0-570.21.1.el9_6, python3-perf 5.14.0-570.21.1.el9_6, kernel-devel-matched 5.14.0-570.21.1.el9_6, kernel-64k-devel-matched 5.14.0-570.21.1.el9_6, +7 more
    fixed: vendor fix RHSA-2025:8643
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-55.16.1.el10_0, perf 6.12.0-55.16.1.el10_0, rtla 6.12.0-55.16.1.el10_0, python3-perf 6.12.0-55.16.1.el10_0, kernel-devel-matched 6.12.0-55.16.1.el10_0, kernel-64k-devel-matched 6.12.0-55.16.1.el10_0, +7 more
    fixed: vendor fix RHSA-2025:8669
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-570.21.1.el9_6, kernel-64k 5.14.0-570.21.1.el9_6, kernel-core 5.14.0-570.21.1.el9_6, kernel-tools 5.14.0-570.21.1.el9_6, kernel-modules 5.14.0-570.21.1.el9_6, kernel-64k-core 5.14.0-570.21.1.el9_6, +27 more
    fixed: vendor fix RHSA-2025:8643
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-55.16.1.el10_0, kernel-64k 6.12.0-55.16.1.el10_0, kernel-core 6.12.0-55.16.1.el10_0, kernel-tools 6.12.0-55.16.1.el10_0, kernel-modules 6.12.0-55.16.1.el10_0, kernel-64k-core 6.12.0-55.16.1.el10_0, +27 more
    fixed: vendor fix RHSA-2025:8669
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-570.21.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.21.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.21.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.21.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.21.1.el9_6
    fixed: vendor fix RHSA-2025:8643
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-55.16.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.16.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.16.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.16.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.16.1.el10_0
    fixed: vendor fix RHSA-2025:8669
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-570.21.1.el9_6, kernel-rt-64k 5.14.0-570.21.1.el9_6, kernel-rt-core 5.14.0-570.21.1.el9_6, kernel-rt-modules 5.14.0-570.21.1.el9_6, kernel-rt-64k-core 5.14.0-570.21.1.el9_6, kernel-rt-debug-core 5.14.0-570.21.1.el9_6, +14 more
    fixed: vendor fix RHSA-2025:8643
show 4 more
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-55.16.1.el10_0, kernel-rt-64k 6.12.0-55.16.1.el10_0, kernel-rt-core 6.12.0-55.16.1.el10_0, kernel-rt-modules 6.12.0-55.16.1.el10_0, kernel-rt-64k-core 6.12.0-55.16.1.el10_0, kernel-rt-debug-core 6.12.0-55.16.1.el10_0, +14 more
    fixed: vendor fix RHSA-2025:8669
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-570.21.1.el9_6, kernel-rt-kvm 5.14.0-570.21.1.el9_6, kernel-rt-core 5.14.0-570.21.1.el9_6, kernel-rt-modules 5.14.0-570.21.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.21.1.el9_6, kernel-rt-debug-core 5.14.0-570.21.1.el9_6, +6 more
    fixed: vendor fix RHSA-2025:8643
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-55.16.1.el10_0, kernel-rt-kvm 6.12.0-55.16.1.el10_0, kernel-rt-core 6.12.0-55.16.1.el10_0, kernel-rt-modules 6.12.0-55.16.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.16.1.el10_0, kernel-rt-debug-core 6.12.0-55.16.1.el10_0, +6 more
    fixed: vendor fix RHSA-2025:8669
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 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 ICSA-26-295-11 updated cvss 7.8

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.7 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.7
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-26-209-04 updated cvss 5.5

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.6 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.6
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 15% 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 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
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

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.