CVE-2026-98978 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, Linux distribution maintainers, and users of Linux-based systems, as well as operators, platform administrators, vulnerability management teams, and security teams who need to assess their exposure and apply patches or mitigations as necessary.

Why it matters

This vulnerability could allow an attacker to potentially reveal underlying files and directories, leading to unauthorized access or exposure of sensitive data. Linux kernel developers and maintainers, Linux distribution maintainers, and users of Linux-based systems should assess their exposure and apply patches or mitigations as necessary.

• Potential exposure of sensitive data
• Potential unauthorized access to files and directories
• Potential disruption of service due to exploitation

Technical summary

The vulnerability is caused by the fact that locked mounts are special and protect the underlying files and directories from being revealed. However, the shrink_submounts function does not handle locked mounts correctly, allowing a shrinkable mount to become locked and be placed beneath another locked mount. This can lead to a situation where a locked mount is expired, potentially revealing underlying files and directories. The vulnerability has been resolved in the Linux kernel, and affected versions are 5ff9d8a65ce80efb509ce4e8051394e9ed2cd942 and less than 6b8dc3713a76346d212abab46cbfc8d7070f534c, 5ff9d8a65ce80efb509ce4e8051394e9ed2cd942 and less than d23265a12e4991ce7aedce670c0b6b598cadb644, and 5ff9d8a65ce

Defensive priority

Medium

Recommended defensive actions

• Review and apply the patches provided by the Linux kernel maintainers.
• Ensure that the Linux kernel is updated to a version that includes the fix.
• Monitor the system for any potential exploitation attempts.
• 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.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.

Evidence notes

The vulnerability was introduced in the Linux kernel and has been resolved. The affected versions are 5ff9d8a65ce80efb509ce4e8051394e9ed2cd942 and less than 6b8dc3713a76346d212abab46cbfc8d7070f534c, 5ff9d8a65ce80efb509ce4e8051394e9ed2cd942 and less than d23265a12e4991ce7aedce670c0b6b598cadb644, and 5ff9d8a65ce80efb509ce4e8051394e9ed2cd942 and less than f78ddcc872248c7aa1d7e904928441a0be4c6d5d.

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.