CVE-2026-98745 Linux CVE debrief

Who should care

Linux kernel maintainers, users, and administrators should assess exposure and verify the presence of the fix in their kernel versions to prevent fatal EL1 UNDEFs. Affected operators, platforms, and security teams should review kernel versions, assess system configurations, and apply the fix if necessary.

Why it matters

A vulnerability in the Linux kernel's arm64/fpsimd signal handling can cause a task to erroneously have non-streaming SVE state, leading to fatal EL1 UNDEFs. Linux kernel maintainers and users should assess exposure and verify the presence of the fix in their kernel versions.

• Verify kernel versions for the presence of the fix
• Assess system configurations for potential impact
• Apply the fix if necessary to prevent fatal EL1 UNDEFs

Technical summary

The Linux kernel's arm64/fpsimd signal handling has a vulnerability that can cause a task to erroneously have non-streaming SVE state when system_supports_sme() is true but system_supports_sve() is false. This can lead to fatal EL1 UNDEFs. The restore_sve_fpsimd_context() function has been reworked to reject cases where SVE_SIG_FLAG_SM is clear and an SVE payload is present. Linux kernel maintainers and users should assess exposure and verify the presence of the fix in their kernel versions to prevent fatal EL1 UNDEFs.

Defensive priority

Linux kernel maintainers and users should assess exposure and verify the presence of the fix in their kernel versions.

Recommended defensive actions

• Review kernel versions for the presence of the fix
• Assess exposure and apply the fix if necessary
• Verify system configurations for potential impact
• 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
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed

Evidence notes

The CVE record and source references provide details on the vulnerability and its fix. The NVD entry is currently null. Linux kernel maintainers and users should verify kernel versions for the presence of the fix and assess exposure. The vulnerability can cause a task to erroneously have non-streaming SVE state, leading to fatal EL1 UNDEFs. Evidence is limited to CVE and NVD entries.

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.