CVE-2025-21993 json
iscsi_ibft: Fix UBSAN shift-out-of-bounds warning in ibft_attr_show_nic()
published 2025-04-02 19 mo ago modified 2026-06-17 4 mo ago also EUVD-2025-9544
- cvss
- 7.1
- 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 12%
- public exploits
- 0
- none known
Summary
In the Linux kernel, the following vulnerability has been resolved:
iscsi_ibft: Fix UBSAN shift-out-of-bounds warning in ibft_attr_show_nic()
When performing an iSCSI boot using IPv6, iscsistart still reads the /sys/firmware/ibft/ethernetX/subnet-mask entry. Since the IPv6 prefix length is 64, this causes the shift exponent to become negative, triggering a UBSAN warning. As the concept of a subnet mask does not apply to IPv6, the value is set to ~0 to suppress the warning message.
Patch / fix
- Linux Linux 5.4.292, 5.10.236, 5.15.180, 6.1.132, 6.6.84, 6.12.20, 6.13.8, 6.14
- linux Debian 12 6.1.133-1
- linux Debian 14, Debian 13 6.12.20-1
debian advisories DEBIAN-CVE-2025-21993
- linux Ubuntu 22.04 LTS 5.15.0-138.148
- linux Ubuntu 24.04 LTS 6.8.0-58.60
- linux-aws Ubuntu 22.04 LTS 5.15.0-1082.89
- linux-aws Ubuntu 24.04 LTS 6.8.0-1027.29
- linux-gcp Ubuntu 22.04 LTS 5.15.0-1081.90
- linux-gcp Ubuntu 24.04 LTS 6.8.0-1028.30
- linux-gke Ubuntu 22.04 LTS 5.15.0-1079.85
- linux-gke Ubuntu 24.04 LTS 6.8.0-1023.27
ubuntu advisories UBUNTU-CVE-2025-21993
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 6.12.0-55.12.1.el10_0
- rv RHEL 10.0 6.12.0-55.12.1.el10_0
- perf RHEL 10.0 6.12.0-55.12.1.el10_0
- rtla RHEL 10.0 6.12.0-55.12.1.el10_0
- libperf RHEL 10.0 6.12.0-55.12.1.el10_0
- kernel-rt RHEL 10.0 6.12.0-55.12.1.el10_0
- kernel-64k RHEL 10.0 6.12.0-55.12.1.el10_0
- kernel-core RHEL 10.0 6.12.0-55.12.1.el10_0
red hat advisories RHSA-2025:7956RHSA-2025:7423
- 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-2025:01614-1
- kernel AlmaLinux 9 5.14.0-570.16.1.el9_6
- rv AlmaLinux 9 5.14.0-570.16.1.el9_6
- perf AlmaLinux 9 5.14.0-570.16.1.el9_6
- rtla AlmaLinux 9 5.14.0-570.16.1.el9_6
- libperf AlmaLinux 9 5.14.0-570.16.1.el9_6
- kernel-rt AlmaLinux 9 5.14.0-570.16.1.el9_6
- kernel-64k AlmaLinux 9 5.14.0-570.16.1.el9_6
- kernel-core AlmaLinux 9 5.14.0-570.16.1.el9_6
almalinux advisories ALSA-2025:7423
- kernel Rocky Linux 10 6.12.0-55.12.1.el10_0
rocky linux advisories RLSA-2025:7956
- kernel CBL-Mariner 2.0 5.15.180.1-1
- kernel Azure Linux 3.0 6.6.85.1-2
azure linux advisories AZL-59769AZL-59892
Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT
- git.kernel.org/stable/c/a858cd58dea06cf85b142673deea8c5d87f11e70 commit
- git.kernel.org/stable/c/f763c82db8166e28f45b7cc4a5398a7859665940 commit
- git.kernel.org/stable/c/b388e185bfad32bfed6a97a6817f74ca00a4318f commit
- git.kernel.org/stable/c/9bfa80c8aa4e06dff55a953c3fffbfc68a3a3b1c commit
- git.kernel.org/stable/c/2d1eef248107bdf3d5a69d0fde04c30a79a7bf5d commit
- git.kernel.org/stable/c/b253660fac5e0e9080d2c95e3a029e1898d49afb commit
- git.kernel.org/stable/c/c1c6e527470e5eab0b2d57bd073530fbace39eab commit
- git.kernel.org/stable/c/07e0d99a2f701123ad3104c0f1a1e66bce74d6e5 commit
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-2025-21993 updated cvss 7.1
kernel: iscsi_ibft: Fix UBSAN shift-out-of-bounds warning in ibft_attr_show_nic()
-
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 moreaffected: no fix planned “Out of support scope”
-
Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-570.16.1.el9_6, perf 5.14.0-570.16.1.el9_6, rtla 5.14.0-570.16.1.el9_6, python3-perf 5.14.0-570.16.1.el9_6, kernel-devel-matched 5.14.0-570.16.1.el9_6, kernel-64k-devel-matched 5.14.0-570.16.1.el9_6, +7 morefixed: vendor fix RHSA-2025:7423
-
Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-55.12.1.el10_0, perf 6.12.0-55.12.1.el10_0, rtla 6.12.0-55.12.1.el10_0, python3-perf 6.12.0-55.12.1.el10_0, kernel-devel-matched 6.12.0-55.12.1.el10_0, kernel-64k-devel-matched 6.12.0-55.12.1.el10_0, +7 morefixed: vendor fix RHSA-2025:7956
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Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-570.16.1.el9_6, kernel-64k 5.14.0-570.16.1.el9_6, kernel-core 5.14.0-570.16.1.el9_6, kernel-tools 5.14.0-570.16.1.el9_6, kernel-modules 5.14.0-570.16.1.el9_6, kernel-64k-core 5.14.0-570.16.1.el9_6, +27 morefixed: vendor fix RHSA-2025:7423
-
Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-55.12.1.el10_0, kernel-64k 6.12.0-55.12.1.el10_0, kernel-core 6.12.0-55.12.1.el10_0, kernel-tools 6.12.0-55.12.1.el10_0, kernel-modules 6.12.0-55.12.1.el10_0, kernel-64k-core 6.12.0-55.12.1.el10_0, +27 morefixed: vendor fix RHSA-2025:7956
-
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-570.16.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.16.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.16.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.16.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.16.1.el9_6fixed: vendor fix RHSA-2025:7423
-
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-55.12.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.12.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.12.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.12.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.12.1.el10_0fixed: vendor fix RHSA-2025:7956
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Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-570.16.1.el9_6, kernel-rt-64k 5.14.0-570.16.1.el9_6, kernel-rt-core 5.14.0-570.16.1.el9_6, kernel-rt-modules 5.14.0-570.16.1.el9_6, kernel-rt-64k-core 5.14.0-570.16.1.el9_6, kernel-rt-debug-core 5.14.0-570.16.1.el9_6, +14 morefixed: vendor fix RHSA-2025:7423
show 3 moreshow fewer
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Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-55.12.1.el10_0, kernel-rt-64k 6.12.0-55.12.1.el10_0, kernel-rt-core 6.12.0-55.12.1.el10_0, kernel-rt-modules 6.12.0-55.12.1.el10_0, kernel-rt-64k-core 6.12.0-55.12.1.el10_0, kernel-rt-debug-core 6.12.0-55.12.1.el10_0, +14 morefixed: vendor fix RHSA-2025:7956
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Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-570.16.1.el9_6, kernel-rt-kvm 5.14.0-570.16.1.el9_6, kernel-rt-core 5.14.0-570.16.1.el9_6, kernel-rt-modules 5.14.0-570.16.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.16.1.el9_6, kernel-rt-debug-core 5.14.0-570.16.1.el9_6, +6 morefixed: vendor fix RHSA-2025:7423
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Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-55.12.1.el10_0, kernel-rt-kvm 6.12.0-55.12.1.el10_0, kernel-rt-core 6.12.0-55.12.1.el10_0, kernel-rt-modules 6.12.0-55.12.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.12.1.el10_0, kernel-rt-debug-core 6.12.0-55.12.1.el10_0, +6 morefixed: vendor fix RHSA-2025:7956
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
- partial
- Assessed
- 13 mo ago
Exploit prediction
0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CISA ADP | 3.1 | 7.1 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H |
| NVD | 3.1 | 7.1 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H |
| CNA | 3.1 | 7.1 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H |
Affected products
- Linux Linux
Classification
- Weakness
-
- CWE-125 Out-of-bounds Read
- Technology feeds
References
-
git.kernel.org
/stable/c/a858cd58dea06cf85b142673deea8c5d87f11e70
patch
-
git.kernel.org
/stable/c/f763c82db8166e28f45b7cc4a5398a7859665940
patch
-
git.kernel.org
/stable/c/b388e185bfad32bfed6a97a6817f74ca00a4318f
patch
-
git.kernel.org
/stable/c/9bfa80c8aa4e06dff55a953c3fffbfc68a3a3b1c
patch
-
git.kernel.org
/stable/c/2d1eef248107bdf3d5a69d0fde04c30a79a7bf5d
patch
-
git.kernel.org
/stable/c/b253660fac5e0e9080d2c95e3a029e1898d49afb
patch
-
git.kernel.org
/stable/c/c1c6e527470e5eab0b2d57bd073530fbace39eab
patch
-
git.kernel.org
/stable/c/07e0d99a2f701123ad3104c0f1a1e66bce74d6e5
patch
- lists.debian.org /debian-lts-announce/2025/05/msg00045.html
- lists.debian.org /debian-lts-announce/2025/05/msg00030.html
Sources
- CVE List CVE-2025-21993
- NVD CVE-2025-21993
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.