SB20261022128 - Use of Uninitialized Variable in Linux kernel perf_clear_branch_entry_bitfields() and BRBE branch-record handling in drivers/perf/arm_brbe.c

Description

This security bulletin contains information about 1 vulnerability.

1) Use of Uninitialized Variable (CVE-ID: CVE-2026-98551)

CWE-ID: CWE-457 - Use of Uninitialized Variable

CVSSv4: 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]

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.

Remediation

Install update from vendor's website.

References

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