CVE intelligence

CVE-2026-53221

Vulnerability intelligence

Published Jun 25, 2026Sources checked Oct 28, 2026

9.8CRITICALCVSS out of 10

What this means

Review the available evidence

CVE-2026-53221 and is rated Critical severity with a CVSS score of 9.8. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Ubuntu Security Notices guidance

Vendor revision: Oct 15, 2026

Vendor remediation details

This update corrects flaws in the following subsystems: - S390 architecture; - IIO ADC drivers; - Multiple devices driver; - PCI subsystem; - VFIO drivers; - Network file system (NFS) server daemon; - Overlay file system; - IPv6 networking; - Netfilter; (CVE-2024-53194, CVE-2024-53214, CVE-2024-56570, CVE-2024-56779, CVE-2024-57849, CVE-2024-57904, CVE-2024-57929, CVE-2025-21664, CVE-2025-38724, CVE-2026-53131, CVE-2026-53221)

Ubuntu Security Notices guidance

Vendor revision: Oct 13, 2026

Vendor remediation details

This update corrects flaws in the following subsystems: - Ethernet bonding driver; - Network drivers; - F2FS file system; - Network file system (NFS) server daemon; - Tracing infrastructure; - io_uring subsystem; - Networking core; - IPv6 networking; - IUCV driver; - Netfilter; - RxRPC session sockets; (CVE-2022-49149, CVE-2022-49170, CVE-2022-49182, CVE-2022-49201, CVE-2024-53187, CVE-2024-53210, CVE-2024-56763, CVE-2025-38724, CVE-2026-43456, CVE-2026-52910, CVE-2026-53131, CVE-2026-53221)

Ubuntu Security Notices guidance

Vendor revision: Oct 13, 2026

Vendor remediation details

CISA KEVNot listedBased on the latest collected catalog

EPSS0.6%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-53221?

In the Linux kernel, the following vulnerability has been resolved:

ip6_vti: fix incorrect tunnel matching in vti6_tnl_lookup()

In vti6_tnl_lookup(), when an exact match for a tunnel fails, the code falls back to searching for wildcard tunnels:

- Tunnels matching the packet's local address, with any remote address wildcard remote).

- Tunnels matching the packet's remote address, with any local address (wildcard local).

However, vti6 stores all these different types of tunnels in the same hash table (ip6n->tnls_r_l) prone to hash collisions.

The bug is that the fallback search loops in vti6_tnl_lookup() were missing checks to ensure that the candidate tunnel actually has a wildcard address.

Source: NVD