CVE-2026-68432

In the Linux kernel, the following vulnerability has been resolved:

vxlan: require CAP_NET_ADMIN in the device netns for changelink

A tunnel changelink() operates on at most two netns, dev_net(dev) and the sticky underlay netns vxlan->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 vxlan->net can rewrite a vxlan device whose underlay lives in vxlan->net.

vxlan_changelink() validates and applies the new configuration against vxlan->net (vxlan_config_validate(vxlan->net, …)) and can reopen the underlay socket in that netns, so the same reasoning as the tunnel changelink series applies here.

Gate vxlan_changelink() with rtnl_dev_link_net_capable(), at the top of the op before any attribute is parsed, matching ipgre_changelink() and the rest of the require CAP_NET_ADMIN in the device netns for changelink series.

Found by 0sec automated security-research tooling (https://0sec.ai).

Weakness

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Affected Software

Potential Mitigations

• Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
• Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
• For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
• One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

References

• https://git.kernel.org/stable/c/0aa580a8bbbed2507b4582a1f0ef581d480d06ed
• https://git.kernel.org/stable/c/32d10c46bfde3e9b274e9e1bd6399d0ebea8f60f
• https://git.kernel.org/stable/c/3a61bd9637f3d929aa846e4eb3d98b48c26fcb0e
• https://git.kernel.org/stable/c/730c7e5fea7f06e0cdf21c547222ec93234fd1d6
• https://git.kernel.org/stable/c/7465ade989ba84adc2bfa58bad3ca25d249f0f7a
• https://git.kernel.org/stable/c/b3793d7dccb192ffff29894d11824db6251acdd5
• https://git.kernel.org/stable/c/b95a8743e58f7efed5ddc4cb73829b66f17feab0
• https://git.kernel.org/stable/c/e8ad0d311e225939a9a6c745d6cc384c7364ec87