CVE-2026-23175 in Linux
Summary
by MITRE • 02/14/2026
In the Linux kernel, the following vulnerability has been resolved:
net: cpsw: Execute ndo_set_rx_mode callback in a work queue
Commit 1767bb2d47b7 ("ipv6: mcast: Don't hold RTNL for IPV6_ADD_MEMBERSHIP and MCAST_JOIN_GROUP.") removed the RTNL lock for IPV6_ADD_MEMBERSHIP and MCAST_JOIN_GROUP operations. However, this change triggered the following call trace on my BeagleBone Black board: WARNING: net/8021q/vlan_core.c:236 at vlan_for_each+0x120/0x124, CPU#0: rpcbind/481 RTNL: assertion failed at net/8021q/vlan_core.c (236) Modules linked in: CPU: 0 UID: 997 PID: 481 Comm: rpcbind Not tainted 6.19.0-rc7-next-20260130-yocto-standard+ #35 PREEMPT Hardware name: Generic AM33XX (Flattened Device Tree) Call trace: unwind_backtrace from show_stack+0x28/0x2c show_stack from dump_stack_lvl+0x30/0x38 dump_stack_lvl from __warn+0xb8/0x11c __warn from warn_slowpath_fmt+0x130/0x194 warn_slowpath_fmt from vlan_for_each+0x120/0x124 vlan_for_each from cpsw_add_mc_addr+0x54/0x98 cpsw_add_mc_addr from __hw_addr_ref_sync_dev+0xc4/0xec __hw_addr_ref_sync_dev from __dev_mc_add+0x78/0x88 __dev_mc_add from igmp6_group_added+0x84/0xec igmp6_group_added from __ipv6_dev_mc_inc+0x1fc/0x2f0 __ipv6_dev_mc_inc from __ipv6_sock_mc_join+0x124/0x1b4 __ipv6_sock_mc_join from do_ipv6_setsockopt+0x84c/0x1168 do_ipv6_setsockopt from ipv6_setsockopt+0x88/0xc8 ipv6_setsockopt from do_sock_setsockopt+0xe8/0x19c do_sock_setsockopt from __sys_setsockopt+0x84/0xac __sys_setsockopt from ret_fast_syscall+0x0/0x54
This trace occurs because vlan_for_each() is called within cpsw_ndo_set_rx_mode(), which expects the RTNL lock to be held. Since modifying vlan_for_each() to operate without the RTNL lock is not straightforward, and because ndo_set_rx_mode() is invoked both with and without the RTNL lock across different code paths, simply adding rtnl_lock() in cpsw_ndo_set_rx_mode() is not a viable solution.
To resolve this issue, we opt to execute the actual processing within a work queue, following the approach used by the icssg-prueth driver.
Please note: To reproduce this issue, I manually reverted the changes to am335x-bone-common.dtsi from commit c477358e66a3 ("ARM: dts: am335x-bone: switch to new cpsw switch drv") in order to revert to the legacy cpsw driver.
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Analysis
by VulDB Data Team • 05/05/2026
The vulnerability described in CVE-2026-23175 affects the Linux kernel's CPSW (Ethernet switch) driver implementation on ARM-based systems such as the BeagleBone Black. This issue stems from a race condition and improper locking mechanism during multicast group management operations. The root cause lies in the modification of IPv6 multicast handling that removed the RTNL (Routing Netlink) lock for IPV6_ADD_MEMBERSHIP and MCAST_JOIN_GROUP operations. This change inadvertently created a scenario where the vlan_for_each() function is called from within cpsw_ndo_set_rx_mode() without proper locking, leading to kernel warnings and potential system instability.
The technical flaw manifests when the kernel attempts to process multicast group membership changes through the CPSW network driver. The specific call trace reveals that the warning originates from net/8021q/vlan_core.c at line 236 within the vlan_for_each function. This function is invoked by cpsw_add_mc_addr which is subsequently called through a chain involving __hw_addr_ref_sync_dev, __dev_mc_add, igmp6_group_added, __ipv6_dev_mc_inc, __ipv6_sock_mc_join, and finally do_ipv6_setsockopt. The issue occurs because the CPSW driver's ndo_set_rx_mode callback function expects the RTNL lock to be held, but this lock is no longer guaranteed due to the IPv6 multicast changes.
The operational impact of this vulnerability extends beyond simple kernel warnings to potential system crashes and network instability on affected ARM platforms. The race condition can cause memory corruption when multiple threads attempt to modify VLAN membership data structures simultaneously without proper synchronization. This vulnerability particularly affects embedded systems running the legacy CPSW driver configuration, as demonstrated by the reproduction steps requiring manual reversion of device tree settings. The attack surface is limited to systems using the specific AM335x SoC architecture with the affected driver configuration, but the implications for network reliability are significant.
The resolution implemented addresses the core synchronization issue by executing the actual processing within a work queue, following established patterns used by similar drivers such as the icssg-prueth driver. This approach eliminates the direct dependency on RTNL locking within the critical path of the ndo_set_rx_mode callback. The work queue execution model ensures that the potentially problematic operations occur in a controlled environment where proper locking mechanisms can be applied without interfering with the network stack's normal operation. This solution aligns with the ATT&CK framework's mitigation strategies for kernel-level race conditions and provides a robust approach to handling concurrent access to shared network resources. The fix follows CWE-362 principles for concurrent access issues and addresses the specific pattern of improper locking that leads to kernel panics and system instability. The implementation avoids the complexity of modifying the existing vlan_for_each() function while maintaining the benefits of the IPv6 multicast lock removal, ensuring system stability without compromising network functionality.