Use of Uninitialized Variable in Linux kernel - CVE-2026-64220

Vulnerability identifier: #VU139788

CSH Severity: Low

CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-64220

CWE-ID: CWE-457

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to use of uninitialized memory in fwnode_init() when initializing a firmware node allocated on the stack or with a non-zeroing heap allocation. A local user can trigger code paths that dereference the uninitialized secondary pointer to cause a denial of service.

The issue can occur when a temporary software node is used and its lifetime is controlled by the caller.

Linux kernel
Ubuntu
linux-intel-iot-realtime (Ubuntu package)
linux-intel-iotg (Ubuntu package)
linux-azure-5.15 (Ubuntu package)
linux-gcp-5.15 (Ubuntu package)
linux-azure-fips (Ubuntu package)
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp-7.0 (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
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-intel-iotg (Ubuntu package) - addressed in versions 5.15.0.1107.106, 5.15.0-1107.113
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-gcp-5.15 (Ubuntu package) - update to 5.15.0-1112.122~20.04.1
linux-azure-fips (Ubuntu package) - addressed in versions 5.15.0.1117.102, 5.15.0-1117.126+fips1
linux (Ubuntu package) - addressed in versions 6.8.0-139.139+fips1, 6.8.0-1049.53, 6.8.0-1062.65+fips1, 6.8.0-1062.65.1, 6.8.0-1062.65~22.04.1, 6.8.0-1062.70, 6.8.0-1064.68, 6.8.0-1067.75, 6.8.0-1067.75+fips1, 6.8.1-1059.60, 6.8.1-1059.60~22.04.1
linux-aws (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1015.15
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
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/215c90ee656114f5e8c32408228d97082f8e0eef
• https://git.kernel.org/stable/c/34bf74b1fd2e4a44e27821a329204caf09df2976
• https://git.kernel.org/stable/c/371f53925a6714d0aa35f1aefdffc3e8cd62f480
• https://git.kernel.org/stable/c/3f1024deeab3b5443c29b3de4fe475e87309b8fa
• https://git.kernel.org/stable/c/508fd8ab158abd04b7f7d0f707cd6d6c405df4ea
• https://git.kernel.org/stable/c/f0e211d6539fae800217c10797993b7592d6ab01
• https://git.kernel.org/stable/c/f59e686c778cb41b8f7aa8fab2afd6a01afb3d47

• Use of Uninitialized Variable in Linux kernel fwnode_init()
• Ubuntu update for linux-azure-5.15
• Ubuntu update for linux-aws
• Ubuntu update for linux-azure-fips
• Ubuntu update for linux-intel-iot-realtime
• Ubuntu update for linux-intel-iotg
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia
• Ubuntu update for linux-gcp-5.15
• Ubuntu update for linux
• Ubuntu update for linux-gcp-7.0