Uncontrolled Recursion in Linux kernel - CVE-2026-63891

Vulnerability identifier: #VU138758

CSH Severity: Medium

CVSS v4: 7.1 [CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63891

CWE-ID: CWE-674

Exploitation vector: Adjecent network

Exploit availability: No public exploit available

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

The vulnerability exists due to uncontrolled recursion in __tb_property_parse_dir() in the thunderbolt property parser when processing a crafted PROPERTIES_REQUEST control-plane exchange containing chained DIRECTORY entries with a back-reference loop. A remote attacker can send crafted XDomain property data to cause a denial of service.

The issue can be triggered by an untrusted XDomain peer such as a cable, dock, in-line inspector, or adjacent host.

Linux kernel
openEuler
Ubuntu
kernel-debuginfo
python3-perf-debuginfo
python3-perf
perf-debuginfo
perf
kernel-tools-devel
kernel-tools-debuginfo
kernel-tools
kernel-source
kernel-headers
kernel-extra-modules
kernel-devel
kernel-debugsource
bpftool-debuginfo
bpftool
kernel
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-debuginfo - update to 6.6.0-145.3.29.160
python3-perf-debuginfo - update to 6.6.0-145.3.29.160
python3-perf - update to 6.6.0-145.3.29.160
perf-debuginfo - update to 6.6.0-145.3.29.160
perf - update to 6.6.0-145.3.29.160
kernel-tools-devel - update to 6.6.0-145.3.29.160
kernel-tools-debuginfo - update to 6.6.0-145.3.29.160
kernel-tools - update to 6.6.0-145.3.29.160
kernel-source - update to 6.6.0-145.3.29.160
kernel-headers - update to 6.6.0-145.3.29.160
kernel-extra-modules - update to 6.6.0-145.3.29.160
kernel-devel - update to 6.6.0-145.3.29.160
kernel-debugsource - update to 6.6.0-145.3.29.160
bpftool-debuginfo - update to 6.6.0-145.3.29.160
bpftool - update to 6.6.0-145.3.29.160
kernel - update to 6.6.0-145.3.29.160
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/0a84ab9271936c11e84e511bb52fc5682f8b6726
• https://git.kernel.org/stable/c/2b5f47a710172c962ef42d1b732b04d2ad0dce21
• https://git.kernel.org/stable/c/830c8a9b467e7d3a158483d37fa7dc13892b293a
• https://git.kernel.org/stable/c/928abe19fbf0127003abcb1ea69cabc1c897d0ab
• https://git.kernel.org/stable/c/95839a67ea56ca35732aad7f711404a3127cfe2d
• https://git.kernel.org/stable/c/b4621e5ef63405c317a84b711faf3bd75b3c6a94
• https://git.kernel.org/stable/c/ed9455ef4bd9babc90f92e526abe3fb68c1a8709
• https://git.kernel.org/stable/c/f31c6d220f455b5af63590302b30e1b932d14599

• Uncontrolled Recursion in Linux kernel thunderbolt driver
• Ubuntu update for linux-ibm
• Ubuntu update for linux-azure
• Ubuntu update for linux-aws
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia
• openEuler 24.03 LTS SP3 update for kernel