CVE-2026-98551 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, as well as users of arm64 systems who need to ensure their kernel is updated with the fix. Additionally, operators and security teams responsible for managing and securing Linux kernel deployments should be aware of this vulnerability and take necessary actions to mitigate its impact. Platform administrators and vulnerability management teams should also review the patch and apply it to affected systems to prevent

Why it matters

A Linux kernel vulnerability was resolved, affecting the perf/core component. The issue involved the clearing of bitfields in struct perf_branch_entry, which was not properly synced with the struct's fields. This resulted in uninitialized data being exposed to userspace on arm64 systems. The fix assigns the whole entry at each site, ensuring all fields are properly cleared. Linux kernel developers and maintainers should review and apply the patch to prevent potential information disclosure or unexpected behavior.

• Uninitialized data exposure to userspace on arm64 systems.
• Potential for information disclosure or unexpected behavior.

Technical summary

The Linux kernel's perf/core component had a vulnerability where the clearing of bitfields in struct perf_branch_entry was not properly synced with the struct's fields. This resulted in uninitialized data being exposed to userspace on arm64 systems. The fix assigns the whole entry at each site, ensuring all fields are properly cleared. The vulnerability was resolved by updating the perf/core component to properly clear the bitfields, preventing potential information disclosure or unexpected behavior. Linux kernel developers and maintainers should review and apply the patch to prevent potential information disclosure or unexpected behavior.

Defensive priority

Medium

Recommended defensive actions

• Review and apply the kernel patch to ensure the perf/core component is updated.
• Verify the system's Linux kernel version and check for any existing fixes or mitigations.
• Monitor system logs for any suspicious activity related to the perf/core component.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but the impact and affected versions require further verification. The Linux kernel's perf/core component is affected, and arm64 systems are specifically impacted.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.