Use of Uninitialized Variable in Linux kernel - CVE-2026-98551

Vulnerability identifier: #VU156854

CSH Severity: Low

CVSS v4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-98551

CWE-ID: CWE-457

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to disclose limited amounts of uninitialized kernel heap data through performance-monitoring branch records.

The vulnerability exists due to use of uninitialized bitfields in the Linux kernel perf branch-record handling code when processing BRBE records. A local user can collect branch records containing unrecognized branch types or source-only records to read new_type or priv bitfields that retain uninitialized heap data or values from previous records.

Only arm64 systems are affected; x86 systems are not affected.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
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

• https://git.kernel.org/stable/c/24b620729e53d978b3e425f55bc66efd3bab1f59
• https://git.kernel.org/stable/c/c7de8521947a521b766979ff5c09f66fe905a5bd

• Use of Uninitialized Variable in Linux kernel perf_clear_branch_entry_bitfields() and BRBE branch-record handling in drivers/perf/arm_brbe.c
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more