CVE-2026-63829: 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 c...

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.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

0.12%

2.5th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= b57708add31494175be741ed3fd24023b50c3423, < 19275943d8fe903eb7b9aa53e380e41efd042ada; >= b57708add31494175be741ed3fd24023b50c3423, < 866b0f5ae599490bd496fd84581c68ac8b94e6af; >= b57708add31494175be741ed3fd24023b50c3423, < 92b766fc55156e0da2ecd0c2302c971118f8a229; >= b57708add31494175be741ed3fd24023b50c3423, < e54c05ed3d9c28733fb9e5837219aca3691defa3; >= b57708add31494175be741ed3fd24023b50c3423, < 9831bc9ecb402957810c2045c663fbfe9b09e296; >= b57708add31494175be741ed3fd24023b50c3423, < 1697957eb0971d420dde42862b88eb43506a1105; >= b57708add31494175be741ed3fd24023b50c3423, < 47b5d3d506609b08b2e1f7c14f0b681a1953d572; >= b57708add31494175be741ed3fd24023b50c3423, < 8165f7ff57d9667d2bb477ef6af83ede7fed4ad7
Linux	Linux	3.16

References

Timeline

Published: Jul 19, 2026
Last Modified: Jul 27, 2026
Status: Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-63829?

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.

How severe is CVE-2026-63829?

CVE-2026-63829 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.12% probability of exploitation in the next 30 days.

How do I fix CVE-2026-63829?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

Related CVEs from 2026

View all 2026CVEs →