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Fencer Vulns
high 8.6

CVE-2025-21855 json

ibmvnic: Don't reference skb after sending to VIOS

published 2025-03-12 19 mo ago modified 2026-08-05 3 mo ago also EUVD-2025-7595

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

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

ibmvnic: Don't reference skb after sending to VIOS

Previously, after successfully flushing the xmit buffer to VIOS, the tx_bytes stat was incremented by the length of the skb.

It is invalid to access the skb memory after sending the buffer to the VIOS because, at any point after sending, the VIOS can trigger an interrupt to free this memory. A race between reading skb->len and freeing the skb is possible (especially during LPM) and will result in use-after-free: ================================================================== BUG: KASAN: slab-use-after-free in ibmvnic_xmit+0x75c/0x1808 [ibmvnic] Read of size 4 at addr c00000024eb48a70 by task hxecom/14495 <...> Call Trace: [c000000118f66cf0] [c0000000018cba6c] dump_stack_lvl+0x84/0xe8 (unreliable) [c000000118f66d20] [c0000000006f0080] print_report+0x1a8/0x7f0 [c000000118f66df0] [c0000000006f08f0] kasan_report+0x128/0x1f8 [c000000118f66f00] [c0000000006f2868] __asan_load4+0xac/0xe0 [c000000118f66f20] [c0080000046eac84] ibmvnic_xmit+0x75c/0x1808 [ibmvnic] [c000000118f67340] [c0000000014be168] dev_hard_start_xmit+0x150/0x358 <...> Freed by task 0: kasan_save_stack+0x34/0x68 kasan_save_track+0x2c/0x50 kasan_save_free_info+0x64/0x108 __kasan_mempool_poison_object+0x148/0x2d4 napi_skb_cache_put+0x5c/0x194 net_tx_action+0x154/0x5b8 handle_softirqs+0x20c/0x60c do_softirq_own_stack+0x6c/0x88 <...> The buggy address belongs to the object at c00000024eb48a00 which belongs to the cache skbuff_head_cache of size 224 ==================================================================

Patch / fix

  • Linux Linux 6.1.130, 6.6.80, 6.12.17, 6.13.5, 6.14
  • linux Debian 12 6.1.133-1
  • linux Debian 14, Debian 13 6.12.17-1

debian advisories DEBIAN-CVE-2025-21855

  • linux Ubuntu 22.04 LTS 5.15.0-164.174
  • linux Ubuntu 24.04 LTS 6.8.0-78.78
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1098.105
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1035.37
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1098.107
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1036.38
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1094.100
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1032.36

ubuntu advisories UBUNTU-CVE-2025-21855

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 9 5.14.0-611.5.1.el9_7
  • rv RHEL 9 5.14.0-611.5.1.el9_7
  • perf RHEL 9 5.14.0-611.5.1.el9_7
  • rtla RHEL 9 5.14.0-611.5.1.el9_7
  • libperf RHEL 9 5.14.0-611.5.1.el9_7
  • kernel-rt RHEL 9 5.14.0-611.5.1.el9_7
  • kernel-64k RHEL 9 5.14.0-611.5.1.el9_7
  • kernel-core RHEL 9 5.14.0-611.5.1.el9_7

red hat advisories RHSA-2025:20518RHSA-2025:20095

  • 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-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.3.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.3.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.3.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.3.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.3.1

suse advisories SUSE-SU-2025:01967-1SUSE-SU-2025:01951-1SUSE-SU-2025:01919-1SUSE-SU-2025:20192-1SUSE-SU-2025:20270-1SUSE-SU-2025:20190-1

  • kernel AlmaLinux 10 6.12.0-124.8.1.el10_1
  • rv AlmaLinux 10 6.12.0-124.8.1.el10_1
  • perf AlmaLinux 10 6.12.0-124.8.1.el10_1
  • rtla AlmaLinux 10 6.12.0-124.8.1.el10_1
  • libperf AlmaLinux 10 6.12.0-124.8.1.el10_1
  • kernel-rt AlmaLinux 10 6.12.0-124.8.1.el10_1
  • kernel-64k AlmaLinux 10 6.12.0-124.8.1.el10_1
  • kernel-core AlmaLinux 10 6.12.0-124.8.1.el10_1

almalinux advisories ALSA-2025:20095ALSA-2025:20518

  • kernel Rocky Linux 10 6.12.0-124.8.1.el10_1
  • kernel Rocky Linux 9 5.14.0-611.5.1.el9_7

rocky linux advisories RLSA-2025:20095RLSA-2025:20518

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-2025-21855 updated cvss 6.4

kernel: ibmvnic: Don't reference skb after sending to VIOS

  • 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: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-611.5.1.el9_7, perf 5.14.0-611.5.1.el9_7, rtla 5.14.0-611.5.1.el9_7, python3-perf 5.14.0-611.5.1.el9_7, kernel-devel-matched 5.14.0-611.5.1.el9_7, kernel-64k-devel-matched 5.14.0-611.5.1.el9_7, +7 more
    fixed: vendor fix RHSA-2025:20518
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-124.8.1.el10_1, perf 6.12.0-124.8.1.el10_1, rtla 6.12.0-124.8.1.el10_1, python3-perf 6.12.0-124.8.1.el10_1, kernel-devel-matched 6.12.0-124.8.1.el10_1, kernel-64k-devel-matched 6.12.0-124.8.1.el10_1, +7 more
    fixed: vendor fix RHSA-2025:20095
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-611.5.1.el9_7, kernel-64k 5.14.0-611.5.1.el9_7, kernel-core 5.14.0-611.5.1.el9_7, kernel-tools 5.14.0-611.5.1.el9_7, kernel-modules 5.14.0-611.5.1.el9_7, kernel-64k-core 5.14.0-611.5.1.el9_7, +27 more
    fixed: vendor fix RHSA-2025:20518
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-124.8.1.el10_1, kernel-64k 6.12.0-124.8.1.el10_1, kernel-core 6.12.0-124.8.1.el10_1, kernel-tools 6.12.0-124.8.1.el10_1, kernel-modules 6.12.0-124.8.1.el10_1, kernel-64k-core 6.12.0-124.8.1.el10_1, +28 more
    fixed: vendor fix RHSA-2025:20095
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-611.5.1.el9_7, kernel-debuginfo-common-s390x 5.14.0-611.5.1.el9_7, kernel-debuginfo-common-x86_64 5.14.0-611.5.1.el9_7, kernel-debuginfo-common-aarch64 5.14.0-611.5.1.el9_7, kernel-debuginfo-common-ppc64le 5.14.0-611.5.1.el9_7
    fixed: vendor fix RHSA-2025:20518
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-124.8.1.el10_1, kernel-debuginfo-common-s390x 6.12.0-124.8.1.el10_1, kernel-debuginfo-common-x86_64 6.12.0-124.8.1.el10_1, kernel-debuginfo-common-aarch64 6.12.0-124.8.1.el10_1, kernel-debuginfo-common-ppc64le 6.12.0-124.8.1.el10_1
    fixed: vendor fix RHSA-2025:20095
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-611.5.1.el9_7, kernel-rt-64k 5.14.0-611.5.1.el9_7, kernel-rt-core 5.14.0-611.5.1.el9_7, kernel-rt-modules 5.14.0-611.5.1.el9_7, kernel-rt-64k-core 5.14.0-611.5.1.el9_7, kernel-rt-debug-core 5.14.0-611.5.1.el9_7, +14 more
    fixed: vendor fix RHSA-2025:20518
show 4 more
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-124.8.1.el10_1, kernel-rt-64k 6.12.0-124.8.1.el10_1, kernel-rt-core 6.12.0-124.8.1.el10_1, kernel-rt-modules 6.12.0-124.8.1.el10_1, kernel-rt-64k-core 6.12.0-124.8.1.el10_1, kernel-rt-debug-core 6.12.0-124.8.1.el10_1, +14 more
    fixed: vendor fix RHSA-2025:20095
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-611.5.1.el9_7, kernel-rt-core 5.14.0-611.5.1.el9_7, kernel-rt-modules 5.14.0-611.5.1.el9_7, kernel-rt-debug-core 5.14.0-611.5.1.el9_7, kernel-rt-modules-core 5.14.0-611.5.1.el9_7, kernel-rt-debug-modules 5.14.0-611.5.1.el9_7, +4 more
    fixed: vendor fix RHSA-2025:20518
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-124.8.1.el10_1, kernel-rt-core 6.12.0-124.8.1.el10_1, kernel-rt-modules 6.12.0-124.8.1.el10_1, kernel-rt-debug-core 6.12.0-124.8.1.el10_1, kernel-rt-modules-core 6.12.0-124.8.1.el10_1, kernel-rt-debug-modules 6.12.0-124.8.1.el10_1, +4 more
    fixed: vendor fix RHSA-2025:20095
  • 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 SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
19 mo ago

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
CISA ADP 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
CNA 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
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.