GHSA-6WC5-2MJJ-PMR6
Vulnerability from github – Published: 2026-07-19 12:30 – Updated: 2026-07-24 15:32In 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.
{
"affected": [],
"aliases": [
"CVE-2026-63829"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-19T12:16:56Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ip_gre: require CAP_NET_ADMIN in the device netns for changelink\n\nA tunnel changelink() operates on at most two netns, dev_net(dev) and\nthe tunnel link netns t-\u003enet. They differ once the device is created in\nor moved to a netns other than the one the request runs in. The rtnl\nchangelink path checks CAP_NET_ADMIN only against dev_net(dev), so a\ncaller privileged there but not in t-\u003enet can rewrite a tunnel that\nlives in t-\u003enet.\n\nAdd rtnl_dev_link_net_capable() next to rtnl_get_net_ns_capable() in\nnet/core/rtnetlink.c. It requires CAP_NET_ADMIN in the link netns and is\nskipped when the link netns is dev_net(dev), where the rtnl path already\nchecked it. The other patches in this series use the same helper.\n\nGate ipgre_changelink() and erspan_changelink() with it, at the top of\nthe op before any attribute is parsed, because the parsers update live\ntunnel fields first. ipgre_netlink_parms() sets t-\u003ecollect_md before\nip_tunnel_changelink() runs.\n\nCommit 8b484efd5cb4 (\"ip6: vti: Use ip6_tnl.net in\nvti6_siocdevprivate().\") added the same check on the ioctl path. This\nadds it on RTM_NEWLINK.",
"id": "GHSA-6wc5-2mjj-pmr6",
"modified": "2026-07-24T15:32:43Z",
"published": "2026-07-19T12:30:24Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63829"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1697957eb0971d420dde42862b88eb43506a1105"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/19275943d8fe903eb7b9aa53e380e41efd042ada"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/47b5d3d506609b08b2e1f7c14f0b681a1953d572"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8165f7ff57d9667d2bb477ef6af83ede7fed4ad7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/866b0f5ae599490bd496fd84581c68ac8b94e6af"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/92b766fc55156e0da2ecd0c2302c971118f8a229"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9831bc9ecb402957810c2045c663fbfe9b09e296"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e54c05ed3d9c28733fb9e5837219aca3691defa3"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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