Heap-based buffer overflow in Linux kernel - CVE-2026-63887

Vulnerability identifier: #VU138771

CSH Severity: Medium

CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63887

CWE-ID: CWE-122

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to a heap-based buffer overflow in iscsi_encode_text_output() when processing iSCSI login text parameters. A remote attacker can send a specially crafted login request with many minimal key-value pairs to cause a denial of service.

The issue can be triggered by expansion of unknown keys into larger "NotUnderstood" response records during login negotiation.

Linux kernel
Red Hat Enterprise Linux for Real Time
Red Hat Enterprise Linux for Real Time for NFV
Anolis OS
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
openEuler
Ubuntu
kernel-rt (Red Hat package)
kernel-doc
bpftool
kernel
kernel-core
kernel-cross-headers
kernel-debug
kernel-debug-core
kernel-debug-devel
kernel-debug-modules
kernel-debug-modules-extra
kernel-headers
kernel-abi-stablelists
python3-perf
perf
kernel-tools-libs-devel
kernel-tools-libs
kernel-tools
kernel-modules-extra
kernel-modules
kernel-devel
python3-perf-debuginfo
python2-perf-debuginfo
python2-perf
perf-debuginfo
kernel-tools-devel
kernel-tools-debuginfo
kernel-source
bpftool-debuginfo
kernel-debuginfo
kernel-debugsource
kernel-extra-modules
kernel (Red Hat package)
linux-ibm (Ubuntu package)
linux-aws (Ubuntu package)
linux-azure (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-nvidia-bos (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
kernel-rt (Red Hat package) - update to 4.18.0-553.157.1.rt7.498.el8_10
kernel-doc - update to 4.18.0-553.157.1.0.1
bpftool - update to 4.18.0-553.157.1.0.1
kernel - update to 4.18.0-553.157.1.0.1
kernel-core - update to 4.18.0-553.157.1.0.1
kernel-cross-headers - update to 4.18.0-553.157.1.0.1
kernel-debug - update to 4.18.0-553.157.1.0.1
kernel-debug-core - update to 4.18.0-553.157.1.0.1
kernel-debug-devel - update to 4.18.0-553.157.1.0.1
kernel-debug-modules - update to 4.18.0-553.157.1.0.1
kernel-debug-modules-extra - update to 4.18.0-553.157.1.0.1
kernel-headers - update to 4.18.0-553.157.1.0.1
kernel-abi-stablelists - update to 4.18.0-553.157.1.0.1
python3-perf - update to 4.18.0-553.157.1.0.1
perf - update to 4.18.0-553.157.1.0.1
kernel-tools-libs-devel - update to 4.18.0-553.157.1.0.1
kernel-tools-libs - update to 4.18.0-553.157.1.0.1
kernel-tools - update to 4.18.0-553.157.1.0.1
kernel-modules-extra - update to 4.18.0-553.157.1.0.1
kernel-modules - update to 4.18.0-553.157.1.0.1
kernel-devel - update to 4.18.0-553.157.1.0.1
perf - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
python3-perf-debuginfo - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
python3-perf - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
python2-perf-debuginfo - update to 4.19.90-2608.2.0.0384
python2-perf - update to 4.19.90-2608.2.0.0384
perf-debuginfo - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-tools-devel - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-tools-debuginfo - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-source - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-tools - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
bpftool - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
bpftool-debuginfo - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-debuginfo - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-debugsource - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-devel - addressed in versions 4.19.90-2608.2.0.0384, 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-headers - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-extra-modules - update to 6.6.0-145.3.29.160
kernel (Red Hat package) - update to 6.12.0-211.47.1.el10_2
linux-ibm (Ubuntu package) - addressed in versions 7.0.0-1008.8, 7.0.0-1010.10
linux-aws (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1015.15
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1010.10
linux-nvidia (Ubuntu package) - addressed in versions 7.0.0-1016.16, 7.0.0-1016.16~24.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2016.16

• https://git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db
• https://git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3
• https://git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b
• https://git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a
• https://git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627
• https://git.kernel.org/stable/c/bf33e01f88388c43e285492a63e539df6ffed64c
• https://git.kernel.org/stable/c/cb84e974fb172bc71386289f37b78ea679410b39
• https://git.kernel.org/stable/c/efe633e600a0ac68357206fede21b1ac8178f3b8

• Heap-based buffer overflow in Linux kernel target iscsi driver
• Ubuntu update for linux-ibm
• Ubuntu update for linux-azure
• Ubuntu update for linux-aws
• openEuler 22.03 LTS SP4 update for kernel
• openEuler 20.03 LTS SP4 update for kernel
• Red Hat Enterprise Linux 10 update for kernel
• Red Hat Enterprise Linux 8 update for kernel-rt
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia
• Anolis OS update for kernel:4.18
• openEuler 24.03 LTS SP3 update for kernel