CVE-2026-98551

/// Technical description

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

perf/core: Fill branch entries with a single assignment

perf_clear_branch_entry_bitfields() clears the bitfields of struct

perf_branch_entry one by one and leaves from/to alone, since callers

overwrite those straight away. The list has to be kept in sync with the

struct by hand and has already fallen behind: new_type and priv were

added to perf_branch_entry and never added here.

Only BRBE writes those two, and neither for every record.

brbe_set_perf_entry_type() leaves new_type alone for a branch type it

does not recognise, and priv is not set for source-only records.

arm_pmuv3.c allocates the per-CPU branch stack with kmalloc(), so such a

record reaches userspace with whatever the slot held: uninitialised

kmalloc() data on the first pass over the buffer, the previous record's

values after that. Nothing under arch/x86/events/ writes either field,

so only arm64 is affected.

Assign the whole entry at each site instea

/// 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