Use-after-free in Linux kernel - CVE-2026-89655

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Main Vulnerability Database Vulnerabilities #VU149153

Use-after-free in Linux kernel - CVE-2026-89655

Published: September 12, 2026


Vulnerability identifier: #VU149153
CSH Severity: Low
CVSS v4: 0 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-89655
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to trigger a use-after-free condition.

The vulnerability exists due to use-after-free in __kick_flushing_caps() when processing FLUSH_ACK messages during cap flushing. A remote attacker can send a FLUSH_ACK message during cap flushing to trigger a use-after-free condition.

Exploitation requires the FLUSH_ACK to be processed after i_ceph_lock is released and before list iteration resumes.


Affected software

Linux kernel
Debian Linux
SUSE Linux Micro
SUSE Linux Micro Extras
Ubuntu
openEuler
linux (Ubuntu package)
linux-kvm (Ubuntu package)
linux-gcp (Ubuntu package)
linux-aws (Ubuntu package)
linux-azure (Ubuntu package)
linux-oracle (Ubuntu package)
linux-lowlatency (Ubuntu package)
linux-gke (Ubuntu package)
linux-aws-5.15 (Ubuntu package)
linux-lowlatency-hwe-5.15 (Ubuntu package)
linux-hwe-5.15 (Ubuntu package)
linux-fips (Ubuntu package)
linux-azure-5.15 (Ubuntu package)
linux-nvidia-tegra (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-realtime (Ubuntu package)
linux-ibm-5.15 (Ubuntu package)
linux-azure-fde-5.15 (Ubuntu package)
linux-gkeop (Ubuntu package)
linux-intel-iotg (Ubuntu package)
linux-nvidia-tegra-igx (Ubuntu package)
linux-ibm (Ubuntu package)
linux-intel-iotg-5.15 (Ubuntu package)
linux-oracle-5.15 (Ubuntu package)
linux-gcp-5.15 (Ubuntu package)
linux-nvidia-tegra-5.15 (Ubuntu package)
linux-azure-fde (Ubuntu package)
linux-intel-iot-realtime (Ubuntu package)
linux-gcp-fips (Ubuntu package)
linux-aws-fips (Ubuntu package)
linux-azure-fips (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
bpftool
kernel
python3-perf-debuginfo
python3-perf
perf-debuginfo
perf
kernel-tools-devel
kernel-tools-debuginfo
kernel-source
kernel-headers
kernel-devel
kernel-debugsource
kernel-debuginfo
bpftool-debuginfo
kernel-tools
kernel-64kb
kernel-default-debugsource
kernel-obs-build-debugsource
kernel-obs-build
kernel-syms
kernel-default-devel
kernel-64kb-devel
kernel-64kb-debugsource
kernel-default
kernel-default-devel-debuginfo
linux (Debian package)

How to mitigate CVE-2026-89655

Install security update from vendor's repository.

linux (Ubuntu package) - addressed in versions 5.15.0-202.212, 7.0.0-42.42
linux-kvm (Ubuntu package) - update to 5.15.0-1111.116
linux-gcp (Ubuntu package) - addressed in versions 5.15.0-1120.130, 7.0.0-1016.18
linux-aws (Ubuntu package) - addressed in versions 5.15.0-1119.126, 7.0.0-1016.17
linux-azure (Ubuntu package) - update to 5.15.0-1125.134
linux-oracle (Ubuntu package) - addressed in versions 5.15.0-1116.122, 7.0.0-1015.16
linux-lowlatency (Ubuntu package) - update to 5.15.0-197.207
linux-gke (Ubuntu package) - update to 5.15.0-1115.121
linux-aws-5.15 (Ubuntu package) - update to 5.15.0-1119.126~20.04.1
linux-lowlatency-hwe-5.15 (Ubuntu package) - update to 5.15.0-197.207~20.04.1
linux-hwe-5.15 (Ubuntu package) - update to 5.15.0-202.212~20.04.1
linux-fips (Ubuntu package) - update to 5.15.0-202.212+fips1
linux-azure-5.15 (Ubuntu package) - update to 5.15.0-1125.134~20.04.1
linux-nvidia-tegra (Ubuntu package) - addressed in versions 5.15.0-1070.72, 6.8.0-1038.42
linux-nvidia (Ubuntu package) - update to 5.15.0-1114.115
linux-realtime (Ubuntu package) - update to 5.15.0-1118.127
linux-ibm-5.15 (Ubuntu package) - update to 5.15.0-1113.117~20.04.1
linux-azure-fde-5.15 (Ubuntu package) - update to 5.15.0-1124.133~20.04.1
linux-gkeop (Ubuntu package) - update to 5.15.0-1102.110
linux-intel-iotg (Ubuntu package) - update to 5.15.0-1114.120
linux-nvidia-tegra-igx (Ubuntu package) - update to 5.15.0-1059.59
linux-ibm (Ubuntu package) - addressed in versions 5.15.0-1113.117, 7.0.0-1017.17
linux-intel-iotg-5.15 (Ubuntu package) - update to 5.15.0-1114.120~20.04.1
linux-oracle-5.15 (Ubuntu package) - update to 5.15.0-1116.122~20.04.1
linux-gcp-5.15 (Ubuntu package) - update to 5.15.0-1120.130~20.04.1
linux-nvidia-tegra-5.15 (Ubuntu package) - update to 5.15.0-1070.72~20.04.1
linux-azure-fde (Ubuntu package) - update to 5.15.0-1124.133
linux-intel-iot-realtime (Ubuntu package) - update to 5.15.0-1111.115
linux-gcp-fips (Ubuntu package) - update to 5.15.0-1120.130+fips1
linux-aws-fips (Ubuntu package) - update to 5.15.0-1119.126+fips1
linux-azure-fips (Ubuntu package) - update to 5.15.0-1125.134+fips1
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17
bpftool - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
python3-perf-debuginfo - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
python3-perf - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
perf-debuginfo - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
perf - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-tools-devel - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-tools-debuginfo - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-source - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-headers - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-devel - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-debugsource - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-debuginfo - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
bpftool-debuginfo - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-tools - addressed in versions 5.10.0-334.0.0.235, 6.6.0-145.1.28.165
kernel-64kb - update to 6.4.0-159998.55.1
kernel-default-debugsource - update to 6.4.0-159998.55.1
kernel-obs-build-debugsource - update to 6.4.0-159998.55.1
kernel-obs-build - update to 6.4.0-159998.55.1
kernel-syms - update to 6.4.0-159998.55.1
kernel-default-devel - update to 6.4.0-159998.55.1
kernel-64kb-devel - update to 6.4.0-159998.55.1
kernel-64kb-debugsource - update to 6.4.0-159998.55.1
kernel-default - update to 6.4.0-159998.55.1
kernel-default-devel-debuginfo - update to 6.4.0-159998.55.1
linux (Debian package) - update to 6.12.111-1

External References

Related Security Bulletins