CVE-2026-72053 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
net: ipip: require CAP_NET_ADMIN in the device netns for changelink
ipip_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.
Gate ipip_changelink() on rtnl_dev_link_net_capable() at its top, before any attribute is parsed.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability described represents a privilege escalation issue within the Linux kernel's networking subsystem, specifically affecting the ipip (IP in IP) tunneling implementation. This flaw exists in the network namespace management logic where the ipip_changelink() function handles configuration changes for ipip tunnels. The core issue stems from improper capability checking during the network device link change operation, creating a scenario where an attacker with sufficient privileges in one network namespace can manipulate tunnel configurations in another namespace where they lack appropriate permissions.
The technical flaw occurs because the rtnl (netlink) changelink path performs capability checks exclusively against the device's current network namespace dev_net(dev) but fails to validate permissions against the tunnel link's network namespace t->net. This asymmetric validation allows a malicious user with CAP_NET_ADMIN rights in the device's namespace to modify tunnels that reside in different network namespaces where they do not possess adequate privileges. The vulnerability manifests when a tunnel device is created or moved into a network namespace other than where the configuration change request originates, creating a mismatch between the operational context and the permission scope.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables attackers to manipulate network routing configurations across namespace boundaries. In environments utilizing network namespaces for isolation purposes such as containerized applications, virtual machines, or multi-tenant systems, this flaw could allow unauthorized users to modify tunnel parameters, potentially redirecting traffic or creating unauthorized network connections. The risk is particularly significant in cloud computing and infrastructure environments where network namespace separation is critical for security boundaries. This vulnerability aligns with CWE-276 (Incorrect Access Control) and represents a clear violation of the principle of least privilege in kernel space operations.
The proposed mitigation strategy involves implementing early capability checking using rtnl_dev_link_net_capable() at the beginning of the ipip_changelink() function before any attribute parsing occurs. This approach ensures that all necessary permissions are validated upfront, preventing the scenario where a caller can proceed with operations they shouldn't be permitted to perform. The solution follows established kernel security patterns for capability enforcement and aligns with ATT&CK technique T1068 (Local Privilege Escalation) by addressing the root cause of unauthorized network configuration modifications. This fix directly addresses the improper access control mechanism that allowed cross-namespace tunnel manipulation while maintaining the legitimate functionality of ipip tunnel management within properly authorized contexts, thereby strengthening the kernel's network namespace security model and preventing potential lateral movement attacks through compromised network configurations.