Linux Kernel up to 6.12.94/6.18.37/7.1.2/7.2 ip_gre net/core/rtnetlink.c rtnl_dev_link_net_capable collect_md privileges management

Summaryinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.12.94/6.18.37/7.1.2/7.2. This vulnerability affects the function rtnl_dev_link_net_capable of the file net/core/rtnetlink.c of the component ip_gre. Performing a manipulation of the argument collect_md results in privileges management. This vulnerability was named CVE-2026-63829. The attack needs to be approached locally. There is no available exploit.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.12.94/6.18.37/7.1.2/7.2. This affects the function rtnl_dev_link_net_capable of the file net/core/rtnetlink.c of the component ip_gre. The manipulation of the argument collect_md with an unknown input leads to a privileges management vulnerability. CWE is classifying the issue as CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-63829 since 07/19/2026. The exploitability is told to be easy. An attack has to be approached locally. Additional levels of successful authentication are necessary for exploitation. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/19/2026). MITRE ATT&CK project uses the attack technique T1068 for this issue.

Upgrading to version 6.12.95, 6.18.38, 7.1.3 or 7.2-rc1 eliminates this vulnerability.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
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• 6.12.88
• 6.12.89
• 6.12.90
• 6.12.91
• 6.12.92
• 6.12.93
• 6.12.94
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
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• 6.18.35
• 6.18.36
• 6.18.37
• 7.0
• 7.1
• 7.1.0
• 7.1.1
• 7.1.2
• 7.2

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

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