CVE-2026-89984

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

perf/x86/intel: Fix kernel address leakages in LBR stack

Before Arch LBR gained CPL filtering support, a user-only branch stack

could still contain kernel addresses. As a result, kernel branch records

may be exposed to user space even when PERF_SAMPLE_BRANCH_USER is

requested.

For example, on Intel Tiger Lake, the following command can still report

SYSRET/ERET entries with kernel-space from addresses:

$ ./perf record -e cycles:p -o - --branch-filter any,save_type,u -- \

./perf bench syscall basic --loop 1000 | \

./perf script -i - --fields brstack|tr ' ' '\n'| \

grep -E '0x[89a-f][0-9a-f]{15}'

Total time: 0.000 [sec]

0.219000 usecs/op

4,566,210 ops/sec

[ perf record: Woken up 1 times to write data ]

[ perf record: Captured and wrote 0.551 MB - ]

0xffffffff93c001c8/0x7f12a2b1d647/P/-/-/16959/SYSRET/-

0xffffffff93c001c8/0x7f12a2b1d5c2/P/-/-/17535/SYSRET/-

0xffffffff93c01928/0x7f12a2861000/P/-/-/6

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References