CVE-2025-21659

What it actually does

The netlink API for NAPI IDs did not enforce namespace boundaries, allowing a process in one network namespace to reference and interact with NAPI instances owned by a different namespace via napi_by_id and related lookups.

Why it matters to the business

In containerized or multi-tenant Linux environments this flaw can permit unauthorized cross-namespace network device access, increasing risk of lateral movement or privilege escalation; the large number of downstream kernel dependents amplifies exposure across server fleets.

How an attack unfolds

An attacker with a socket in one netns sends crafted netlink requests that resolve NAPI IDs belonging to another netns; related Linux kernel privilege-escalation techniques demonstrated by groups exploiting similar issues (CVE-2025-37797, CVE-2025-37890, CVE-2025-38001) can be chained to obtain elevated capabilities.

How to fix it

Upgrade the Linux kernel to a build containing commit b683ba0df11ff563cc237eb1b74d6adfa77226bf; for the listed Red Hat OpenStack packages apply mariadb-galera 1:5.5.42-5.el7ost or newer packages that incorporate the fixed kernel.

How to confirm the fix worked

Confirm the running kernel contains commit b683ba0df11ff563cc237eb1b74d6adfa77226bf, verify that netlink NAPI operations from one netns no longer succeed against objects in another netns, and re-run any existing namespace isolation test suites.

Typical attack path

1. Obtain initial foothold inside a container or process with limited netns visibility
2. Open a netlink socket and issue NAPI ID lookup or configuration commands
3. Resolve NAPI instances that belong to a different namespace
4. Abuse the resulting handle for further network or device manipulation
5. Escalate to host-level access using follow-on kernel primitives

How to detect it

Review audit logs and netlink trace events for NAPI ID lookups that cross namespace boundaries; correlate with process creation events showing unexpected netns transitions and examine related kernel privilege-escalation artifacts from the listed threat-actor campaigns.

What your security team should do

• Prioritize kernel updates on all multi-tenant and container hosts within the next patching cycle
• Audit netlink usage and namespace separation controls in orchestration platforms
• Monitor for follow-on kernel privilege-escalation activity associated with the listed related CVEs
• Apply the exact fixed versions listed for each affected package before the CISA-style deadlines if the issue is later added to KEV