CVE-2026-53221 ip6_vti: fix incorrect tunnel matching in vti6_tnl_lookup()

What is CVE-2026-53221?

CVE-2026-53221 is a critical vulnerability in Linux kernel, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-20

Which versions are affected by CVE-2026-53221?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-53221?

Apply the vendor's patch.

Is CVE-2026-53221 being exploited?

There is no known exploitation of CVE-2026-53221 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-90807, BELL-CVE-2026-53221, DEBIAN-CVE-2026-53221, GHSA-h3c9-j2j5-6mff, ROOT-OS-DEBIAN-11-CVE-2026-53221, ROOT-OS-DEBIAN-12-CVE-2026-53221 and 3 more.