CVE-2026-74283 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
tipc: require net admin for TIPCv2 netlink mutators
TIPCv2 registers mutating generic-netlink operations without admin permission flags. Generic netlink only checks CAP_NET_ADMIN when an operation sets GENL_ADMIN_PERM or GENL_UNS_ADMIN_PERM, so a local unprivileged process can currently change TIPC state through commands such as TIPC_NL_NET_SET, TIPC_NL_KEY_SET, TIPC_NL_KEY_FLUSH, and bearer enable/disable.
The legacy TIPC netlink API already checks netlink_net_capable(..., CAP_NET_ADMIN) for administrative commands. Give the TIPCv2 mutators the equivalent generic-netlink gate. Use GENL_UNS_ADMIN_PERM, which maps to the same namespace-aware CAP_NET_ADMIN check that netlink_net_capable() performs, so the behaviour matches the legacy path and keeps working for CAP_NET_ADMIN holders in a non-initial user namespace (containers).
A QEMU/KASAN repro run as uid/gid 65534 with zero effective capabilities previously succeeded in changing the network id and node identity, setting and flushing key material, and enabling/disabling a UDP bearer. With this patch applied the same operations fail with -EPERM.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability involves a privilege escalation issue within the Linux kernel's TIPCv2 networking implementation that affects local unprivileged users. This represents a critical security weakness where TIPCv2 netlink operations lack proper administrative permission checks, allowing non-privileged processes to modify core network configuration parameters through specific commands. The flaw exists in how the kernel handles generic netlink protocol operations for TIPCv2, specifically in the registration of mutating operations that should require elevated privileges but currently do not.
The technical root cause stems from improper permission handling in the TIPCv2 subsystem where mutating generic-netlink operations are registered without appropriate admin permission flags. In the Linux kernel's generic netlink framework, operations only enforce CAP_NET_ADMIN checks when explicitly marked with GENL_ADMIN_PERM or GENL_UNS_ADMIN_PERM flags. Without these flags, any local process can execute administrative commands through TIPCv2 netlink interfaces that should be restricted to privileged users. This creates a direct pathway for privilege escalation where unprivileged users can manipulate network state information including network identifiers, node identities, cryptographic key material, and bearer configurations.
The operational impact of this vulnerability is significant as it allows local attackers to perform administrative-level operations on TIPCv2 networks without proper authorization. The specific commands affected include TIPC_NL_NET_SET for network configuration changes, TIPC_NL_KEY_SET for cryptographic key manipulation, TIPC_NL_KEY_FLUSH for clearing key material, and bearer enable/disable functions that control network connectivity. These capabilities can be leveraged to disrupt network operations, potentially leading to denial of service conditions or information disclosure. The vulnerability particularly affects containerized environments where users might have elevated privileges within their namespaces but should not have full administrative control over network subsystems.
The mitigation implemented addresses this by requiring net admin permissions for TIPCv2 netlink mutators through the use of GENL_UNS_ADMIN_PERM flag, which ensures consistent behavior with the legacy TIPC netlink API. This change aligns the TIPCv2 implementation with established kernel security patterns and maintains compatibility with existing CAP_NET_ADMIN holders in non-initial user namespaces. The solution follows established security practices that map directly to CWE-276 (Incorrect Default Permissions) and addresses ATT&CK technique T1068 (Local Privilege Escalation) by preventing unauthorized modification of system network configurations. The patch ensures that operations previously executable by unprivileged users now fail with -EPERM errors, effectively closing the security gap while maintaining backward compatibility for legitimate administrative users.
This vulnerability demonstrates the importance of proper permission checking in kernel subsystems and highlights how seemingly minor implementation details can create significant security risks. The fix represents a standard approach to privilege management that aligns with Linux kernel security best practices and helps maintain the principle of least privilege across network administration functions.