Improper Authentication in Linux kernel - CVE-2026-31773

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Main Vulnerability Database Vulnerabilities #VU128923

Improper Authentication in Linux kernel - CVE-2026-31773

Published: May 2, 2026


Vulnerability identifier: #VU128923
CSH Severity: Medium
CVSS v4: 5.3 [CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-31773
CWE-ID: CWE-287
Exploitation vector: Adjecent network
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to bypass authentication requirements.

The vulnerability exists due to improper authentication state handling in the Bluetooth SMP legacy responder STK handling in smp_random() when processing Just Works or Confirm legacy pairing. A remote attacker can initiate a legacy pairing sequence that results in an unauthenticated STK being stored as authenticated to bypass authentication requirements.

The issue affects the legacy responder path and occurs when high security is requested but the pairing flow does not achieve MITM authentication.


Affected software

Linux kernel
Debian Linux
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Workstation Extension 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise High Availability Extension 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Live Patching
SUSE Real Time Module
Basesystem Module
Development Tools Module
Legacy Module
Public Cloud Module
Ubuntu
openEuler
kgraft-patch-4_12_14-122_320-default
kernel-livepatch-6_4_0-150700_7_67-rt
kernel-livepatch-SLE15-SP7-RT_Update_18-debugsource
kernel-livepatch-6_4_0-150700_7_67-rt-debuginfo
kernel-livepatch-6_4_0-150700_53_73-default-debuginfo
kernel-livepatch-6_4_0-150700_53_73-default
kernel-livepatch-SLE15-SP7_Update_19-debugsource
kernel-default-base
kernel-default-kgraft
kernel-default-man
kernel-devel
kernel-macros
kernel-source
kernel-default-kgraft-devel
kernel-default-devel-debuginfo
kernel-default
gfs2-kmp-default-debuginfo
cluster-md-kmp-default
kernel-syms
ocfs2-kmp-default-debuginfo
gfs2-kmp-default
ocfs2-kmp-default
dlm-kmp-default-debuginfo
kernel-default-debuginfo
dlm-kmp-default
cluster-md-kmp-default-debuginfo
kernel-default-base-debuginfo
kernel-default-debugsource
kernel-default-devel
kernel
kernel-tools
kernel-tools-debuginfo
kernel-tools-devel
perf
bpftool
perf-debuginfo
python3-perf
python3-perf-debuginfo
kernel-headers
kernel-debugsource
bpftool-debuginfo
kernel-debuginfo
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-nvidia-tegra (Ubuntu package)
linux-nvidia-tegra-5.15 (Ubuntu package)
linux-intel-iot-realtime (Ubuntu package)
linux-ibm-5.15 (Ubuntu package)
linux-intel-iotg (Ubuntu package)
linux-azure (Ubuntu package)
linux-azure-5.15 (Ubuntu package)
linux-azure-fips (Ubuntu package)
linux-azure-fde (Ubuntu package)
linux (Debian package)
kernel-rt-devel-debuginfo
kernel-rt
kernel-source-rt
kernel-devel-rt
kernel-rt-debuginfo
dlm-kmp-rt
cluster-md-kmp-rt
kernel-rt-debugsource
ocfs2-kmp-rt-debuginfo
kernel-syms-rt
gfs2-kmp-rt-debuginfo
kernel-rt-devel
dlm-kmp-rt-debuginfo
gfs2-kmp-rt
cluster-md-kmp-rt-debuginfo
ocfs2-kmp-rt
kernel-docs
kernel-default-extra
kernel-default-livepatch-devel
kernel-default-livepatch
kernel-azure
kernel-azure-debuginfo
kernel-azure-devel-debuginfo
kernel-azure-devel
kernel-azure-debugsource
kernel-64kb
kernel-64kb-debugsource
kernel-64kb-devel
kernel-64kb-devel-debuginfo
kernel-64kb-debuginfo
kernel-zfcpdump-debugsource
kernel-zfcpdump-debuginfo
kernel-zfcpdump
kernel-default-extra-debuginfo
kernel-obs-build
kernel-obs-build-debugsource
reiserfs-kmp-default
reiserfs-kmp-default-debuginfo
kernel-extra-modules
linux-fips (Ubuntu package)
linux-hwe-6.8 (Ubuntu package)
linux-ibm (Ubuntu package)
linux-oracle-6.8 (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-aws-6.8 (Ubuntu package)
linux-azure-fde-6.8 (Ubuntu package)
linux-gcp-fips (Ubuntu package)

How to mitigate CVE-2026-31773

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
kgraft-patch-4_12_14-122_320-default - update to 1-8.3.1
kernel-livepatch-6_4_0-150700_7_67-rt - update to 1-150700.1.5.1
kernel-livepatch-SLE15-SP7-RT_Update_18-debugsource - update to 1-150700.1.5.1
kernel-livepatch-6_4_0-150700_7_67-rt-debuginfo - update to 1-150700.1.5.1
kernel-livepatch-6_4_0-150700_53_73-default-debuginfo - update to 1-150700.15.3.4
kernel-livepatch-6_4_0-150700_53_73-default - update to 1-150700.15.3.4
kernel-livepatch-SLE15-SP7_Update_19-debugsource - update to 1-150700.15.3.4
kernel-default-base - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2.150700.17.41.4
kernel-default-kgraft - update to 4.12.14-122.320.1
kernel-default-man - update to 4.12.14-122.320.1
kernel-devel - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.1
kernel-macros - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.1
kernel-source - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.1
kernel-default-kgraft-devel - update to 4.12.14-122.320.1
kernel-default-devel-debuginfo - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
kernel-default - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
gfs2-kmp-default-debuginfo - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
cluster-md-kmp-default - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
kernel-syms - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.1
ocfs2-kmp-default-debuginfo - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
gfs2-kmp-default - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
ocfs2-kmp-default - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
dlm-kmp-default-debuginfo - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
kernel-default-debuginfo - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
dlm-kmp-default - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
cluster-md-kmp-default-debuginfo - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
kernel-default-base-debuginfo - update to 4.12.14-122.320.1
kernel-default-debugsource - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
kernel-default-devel - addressed in versions 4.12.14-122.320.1, 6.4.0-150700.53.73.2
kernel - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
kernel-source - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
kernel-tools - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
kernel-tools-debuginfo - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
kernel-tools-devel - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
perf - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
bpftool - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
perf-debuginfo - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
python3-perf - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
python3-perf-debuginfo - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
kernel-headers - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
kernel-devel - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
kernel-debugsource - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
bpftool-debuginfo - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
kernel-debuginfo - addressed in versions 5.10.0-314.0.0.217, 6.6.0-145.1.14.152, 6.6.0-145.3.14.145
linux (Ubuntu package) - addressed in versions 5.15.0.184.155, 5.15.0-184.194, 5.15.0-184.194~20.04.1, 5.15.0.186.166, 5.15.0-186.196, 5.15.0-186.196~20.04.1, 5.15.0.1075.78, 5.15.0-1075.79, 5.15.0.1095.94, 5.15.0-1095.103, 5.15.0.1104.100, 5.15.0-1104.109, 5.15.0.1108.107, 5.15.0-1108.114, 5.15.0.1111.115, 5.15.0-1111.120+fips1, 5.15.0.1112.102, 5.15.0.1112.109, 5.15.0-1112.122, 5.15.0-1112.122+fips1, 6.8.0-136.136, 6.8.0-1046.50, 6.8.0-1059.67, 6.8.0-1064.72, 6.8.0-1064.72~22.04.1, 6.8.1-1056.57, 6.8.1-1056.57~22.04.2
linux-aws (Ubuntu package) - addressed in versions 5.15.0.186.109, 5.15.0-186.196+fips1, 5.15.0.1106.103, 5.15.0-1106.110, 5.15.0.1107.107, 5.15.0-1107.108, 5.15.0.1112.108, 5.15.0.1112.115, 5.15.0-1112.119, 5.15.0-1112.119+fips1, 5.15.0-1112.119~20.04.1, 6.8.0-1061.64+1
linux-nvidia-tegra (Ubuntu package) - addressed in versions 5.15.0-1053.53, 5.15.0.1053.55, 5.15.0.1064.64, 5.15.0-1064.66
linux-nvidia-tegra-5.15 (Ubuntu package) - update to 5.15.0-1064.66~20.04.1
linux-intel-iot-realtime (Ubuntu package) - addressed in versions 5.15.0-1104.106, 5.15.0.1104.108, 5.15.0-1107.113~20.04.1
linux-ibm-5.15 (Ubuntu package) - update to 5.15.0-1106.110~20.04.1
linux-intel-iotg (Ubuntu package) - addressed in versions 5.15.0.1107.106, 5.15.0-1107.113
linux-azure (Ubuntu package) - addressed in versions 5.15.0.1109.105, 5.15.0-1109.115, 5.15.0.1117.115, 5.15.0-1117.126, 6.8.0-1063.71, 6.8.0-1063.71~22.04.1
linux-azure-5.15 (Ubuntu package) - addressed in versions 5.15.0-1109.115~20.04.1, 5.15.0-1117.126~20.04.1, 5.15.0-1117.126~20.04.2
linux-azure-fips (Ubuntu package) - addressed in versions 5.15.0.1117.102, 5.15.0-1117.126+fips1, 6.8.0-1063.71+fips2
linux-azure-fde (Ubuntu package) - addressed in versions 5.15.0-1117.126, 6.8.0-1062.69
linux (Debian package) - update to 6.1.170-1
kernel-rt-devel-debuginfo - update to 6.4.0-150700.7.67.1
kernel-rt - update to 6.4.0-150700.7.67.1
kernel-source-rt - update to 6.4.0-150700.7.67.1
kernel-devel-rt - update to 6.4.0-150700.7.67.1
kernel-rt-debuginfo - update to 6.4.0-150700.7.67.1
dlm-kmp-rt - update to 6.4.0-150700.7.67.1
cluster-md-kmp-rt - update to 6.4.0-150700.7.67.1
kernel-rt-debugsource - update to 6.4.0-150700.7.67.1
ocfs2-kmp-rt-debuginfo - update to 6.4.0-150700.7.67.1
kernel-syms-rt - update to 6.4.0-150700.7.67.1
gfs2-kmp-rt-debuginfo - update to 6.4.0-150700.7.67.1
kernel-rt-devel - update to 6.4.0-150700.7.67.1
dlm-kmp-rt-debuginfo - update to 6.4.0-150700.7.67.1
gfs2-kmp-rt - update to 6.4.0-150700.7.67.1
cluster-md-kmp-rt-debuginfo - update to 6.4.0-150700.7.67.1
ocfs2-kmp-rt - update to 6.4.0-150700.7.67.1
kernel-docs - update to 6.4.0-150700.53.73.1
kernel-default-extra - update to 6.4.0-150700.53.73.2
kernel-default-livepatch-devel - update to 6.4.0-150700.53.73.2
kernel-default-livepatch - update to 6.4.0-150700.53.73.2
kernel-azure - update to 6.4.0-150700.53.73.2
kernel-azure-debuginfo - update to 6.4.0-150700.53.73.2
kernel-azure-devel-debuginfo - update to 6.4.0-150700.53.73.2
kernel-azure-devel - update to 6.4.0-150700.53.73.2
kernel-azure-debugsource - update to 6.4.0-150700.53.73.2
kernel-64kb - update to 6.4.0-150700.53.73.2
kernel-64kb-debugsource - update to 6.4.0-150700.53.73.2
kernel-64kb-devel - update to 6.4.0-150700.53.73.2
kernel-64kb-devel-debuginfo - update to 6.4.0-150700.53.73.2
kernel-64kb-debuginfo - update to 6.4.0-150700.53.73.2
kernel-zfcpdump-debugsource - update to 6.4.0-150700.53.73.2
kernel-zfcpdump-debuginfo - update to 6.4.0-150700.53.73.2
kernel-zfcpdump - update to 6.4.0-150700.53.73.2
kernel-default-extra-debuginfo - update to 6.4.0-150700.53.73.2
kernel-obs-build - update to 6.4.0-150700.53.73.2
kernel-obs-build-debugsource - update to 6.4.0-150700.53.73.2
reiserfs-kmp-default - update to 6.4.0-150700.53.73.2
reiserfs-kmp-default-debuginfo - update to 6.4.0-150700.53.73.2
kernel-extra-modules - update to 6.6.0-145.3.14.145
linux-fips (Ubuntu package) - addressed in versions 6.8.0-136.136+fips2, 6.8.0-136.136.2, 6.8.0-136.136.2~22.04.1, 6.8.0-1058.61
linux-hwe-6.8 (Ubuntu package) - update to 6.8.0-136.136~22.04.1
linux-ibm (Ubuntu package) - addressed in versions 6.8.0-1030.31, 6.8.0-1033.34, 6.8.0-1061.62, 6.8.0-1061.62~22.04.1
linux-oracle-6.8 (Ubuntu package) - update to 6.8.0-1058.61~22.04.1
linux-nvidia (Ubuntu package) - addressed in versions 6.8.0-1059.62, 6.8.0-1059.62.1, 6.8.0-1059.62~22.04.1
linux-aws-6.8 (Ubuntu package) - addressed in versions 6.8.0-1061.64+fips1, 6.8.0-1061.64~22.04.1
linux-azure-fde-6.8 (Ubuntu package) - update to 6.8.0-1062.69~22.04.1
linux-gcp-fips (Ubuntu package) - update to 6.8.0-1064.72+fips1

External References

Related Security Bulletins