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CVE-2026-89984 Affecting linux-6.12 package, versions <6.12.111-1~deb12u1

Severity

 Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.21% (12th percentile)

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  • Snyk IDSNYK-DEBIAN12-LINUX612-20507094
  • published5 Oct 2026
  • disclosed16 Sept 2026
Report a new vulnerability Found a mistake?

Introduced: 16 Sep 2026

NewCVE-2026-89984  (opens in a new tab)

How to fix?

Upgrade Debian:12 linux-6.12 to version 6.12.111-1~deb12u1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream linux-6.12 package and not the linux-6.12 package as distributed by Debian. See How to fix? for Debian:12 relevant fixed versions and status.

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/-/-/6719/ERET/- 0xffffffff93c01928/0x7f12a297a000/P/-/-/8575/ERET/-

The problem is that intel_pmu_lbr_filter() does not fully validate the privilege level of sampled entries. It filters some mismatches based on the branch type and the to address, but it does not reject entries whose from address violates the requested branch privilege filter.

Fix this by extending software filtering to validate both from and to addresses against br_sel. Any LBR entry contains kernel address does not match the requested user filter is dropped. This prevents kernel addresses from appearing in user-only branch stacks.