CVE-2025-71091 in Linux
Summary
by MITRE • 01/13/2026
In the Linux kernel, the following vulnerability has been resolved:
team: fix check for port enabled in team_queue_override_port_prio_changed()
There has been a syzkaller bug reported recently with the following trace:
list_del corruption, ffff888058bea080->prev is LIST_POISON2 (dead000000000122) ------------[ cut here ]------------
kernel BUG at lib/list_debug.c:59! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 3 UID: 0 PID: 21246 Comm: syz.0.2928 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:__list_del_entry_valid_or_report+0x13e/0x200 lib/list_debug.c:59 Code: 48 c7 c7 e0 71 f0 8b e8 30 08 ef fc 90 0f 0b 48 89 ef e8 a5 02 55 fd 48 89 ea 48 89 de 48 c7 c7 40 72 f0 8b e8 13 08 ef fc 90 <0f> 0b 48 89 ef e8 88 02 55 fd 48 89 ea 48 b8 00 00 00 00 00 fc ff RSP: 0018:ffffc9000d49f370 EFLAGS: 00010286 RAX: 000000000000004e RBX: ffff888058bea080 RCX: ffffc9002817d000 RDX: 0000000000000000 RSI: ffffffff819becc6 RDI: 0000000000000005 RBP: dead000000000122 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000080000000 R11: 0000000000000001 R12: ffff888039e9c230 R13: ffff888058bea088 R14: ffff888058bea080 R15: ffff888055461480 FS: 00007fbbcfe6f6c0(0000) GS:ffff8880d6d0a000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c3afcb0 CR3: 00000000382c7000 CR4: 0000000000352ef0 Call Trace: <TASK> __list_del_entry_valid include/linux/list.h:132 [inline]
__list_del_entry include/linux/list.h:223 [inline]
list_del_rcu include/linux/rculist.h:178 [inline]
__team_queue_override_port_del drivers/net/team/team_core.c:826 [inline]
__team_queue_override_port_del drivers/net/team/team_core.c:821 [inline]
team_queue_override_port_prio_changed drivers/net/team/team_core.c:883 [inline]
team_priority_option_set+0x171/0x2f0 drivers/net/team/team_core.c:1534 team_option_set drivers/net/team/team_core.c:376 [inline]
team_nl_options_set_doit+0x8ae/0xe60 drivers/net/team/team_core.c:2653 genl_family_rcv_msg_doit+0x209/0x2f0 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x55c/0x800 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2552 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0xa98/0xc70 net/socket.c:2630 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2684 __sys_sendmsg+0x16d/0x220 net/socket.c:2716 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f
The problem is in this flow: 1) Port is enabled, queue_id != 0, in qom_list 2) Port gets disabled -> team_port_disable() -> team_queue_override_port_del() -> del (removed from list) 3) Port is disabled, queue_id != 0, not in any list 4) Priority changes -> team_queue_override_port_prio_changed() -> checks: port disabled && queue_id != 0 -> calls del - hits the BUG as it is removed already
To fix this, change the check in team_queue_override_port_prio_changed() so it returns early if port is not enabled.
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Analysis
by VulDB Data Team • 03/31/2026
The vulnerability described in CVE-2025-71091 resides within the Linux kernel's team driver implementation, specifically in the function team_queue_override_port_prio_changed(). This issue manifests as a kernel panic due to a list corruption scenario that arises from improper handling of port state transitions during dynamic team configuration changes. The problem was identified through syzkaller, an automated fuzzer, which revealed a critical flaw in how the kernel manages port queue overrides when ports are disabled and re-enabled under specific conditions. The root cause stems from a race condition in list management where a port that has been removed from the queue override list is subsequently attempted to be deleted again during a priority change operation. The kernel's list debugging infrastructure detects this corruption and triggers a BUG at lib/list_debug.c:59, indicating that the list_del operation is being performed on an already deleted entry.
The technical flaw occurs within the team driver's queue override mechanism where ports can be in various states including enabled, disabled, or transitioning. When a port is disabled, it is removed from the qom_list through the team_queue_override_port_del() function, which correctly removes the port from the list structure. However, during subsequent priority change operations, the function team_queue_override_port_prio_changed() fails to properly validate the port's current state before attempting to perform list operations. This function incorrectly assumes that a port that was previously removed from the list can still be processed, leading to a double deletion attempt that corrupts the kernel's internal list structures. The corruption is signaled by the LIST_POISON2 value in the prev pointer, which is a kernel debugging feature designed to detect invalid list pointers after deletion. This particular vulnerability aligns with CWE-457: Use of Uninitialized Variable, as the function operates on a port state that has been improperly validated, and also relates to CWE-129: Improper Validation of Array Index, since the function attempts operations on a list element that may no longer be valid.
The operational impact of this vulnerability is significant, as it can lead to kernel oops, system crashes, and potential denial of service conditions in environments utilizing Linux team drivers for network bonding or link aggregation. Attackers could potentially exploit this vulnerability by triggering specific sequences of port enable/disable operations followed by priority changes, which would cause the kernel to crash and require system reboot. The vulnerability affects systems running Linux kernel versions that include the team driver functionality, particularly those using network teaming configurations where dynamic port management is common. The issue is particularly concerning in high-availability or mission-critical systems where such a kernel panic could result in service disruption. From an attacker's perspective, this vulnerability could be leveraged to perform a denial-of-service attack against systems using team drivers, potentially requiring system administrators to restart services or reboot machines to restore functionality.
The recommended mitigation for this vulnerability involves modifying the team_queue_override_port_prio_changed() function to include an early return check that validates whether the port is actually enabled before proceeding with any list operations. This fix aligns with the ATT&CK technique T1499.004: Endpoint Denial of Service, as it prevents an attacker from exploiting the list corruption to cause system instability. The fix should be implemented by ensuring that the function checks the port's enabled status at the beginning of team_queue_override_port_prio_changed() and returns immediately if the port is not enabled. This change prevents the function from attempting to perform list deletions on ports that have already been removed from the queue override structures, thereby eliminating the list corruption scenario. Additionally, system administrators should ensure that all Linux kernel updates are applied promptly, as this vulnerability is likely to be patched in newer kernel releases. The fix should be part of a broader kernel security hardening strategy that includes regular security audits of network driver components and proper validation of state transitions in kernel subsystems.