Linux kernel flaw affecting container/mount namespaces across distributions; enables local container escape and host file access — widely used infrastructure component.
CVE-2026-98988
Linux kernel mount-namespace bug lets userns processes access covered mounts
Is CVE-2026-98988 being exploited?
Not confirmed. CVE-2026-98988 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.16% probability of exploitation in the next 30 days.
How severe is CVE-2026-98988?
CVE-2026-98988 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-98988?
Yes. A fix has been recorded for CVE-2026-98988. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-98988 affect?
CVE-2026-98988 affects Linux kernel (open_tree / OPEN_TREE_NAMESPACE), Containers and runtimes relying on mount covers (Docker, containerd, CRI-O), Linux hosts running unprivileged user namespaces. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-98988?
Install kernel update with the open_tree namespace fix or disable unprivileged user namespaces (sysctl kernel.unprivileged_userns_clone=0).
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Local privilege escalation: unprivileged user-namespace process can bypass mount covers to read hidden host/container files, enabling container escape and data exposure.
Patch when possible
- affected>= 9b8a0ba68246a61d903ce62c35c303b1501df28b and < b8a94a405ddcf45e9470789e0a821d8f2aa4ca10
- affected>= 9b8a0ba68246a61d903ce62c35c303b1501df28b and < 0febe278ec45b1ccdbe9bd5ff1ba365d8fd55e2a
- affected7.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.