CVE-2025-38324 mpls: Use rcu_dereference_rtnl() in mpls_route_input_rcu().

Medium 5.5 Published 10 Jul 2025 Updated 11 May 2026

A race condition in the Linux kernel MPLS subsystem can trigger a kernel warning and potential denial of service due to incorrect RCU usage.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2025-38324?

CVE-2025-38324 is a medium-severity vulnerability in Debian Debian Linux, published on 10 Jul 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

mpls: Use rcu_dereference_rtnl() in mpls_route_input_rcu().

As syzbot reported [0], mpls_route_input_rcu() can be called from mpls_getroute(), where is under RTNL.

net->mpls.platform_label is only updated under RTNL.

Let's use rcu_dereference_rtnl() in mpls_route_input_rcu() to silence the splat.

[0]: WARNING: suspicious RCU usage 6.15.0-rc7-syzkaller-00082-g5cdb2c77c4c3 #0 Not tainted ---------------------------- net/mpls/af_mpls.c:84 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1 1 lock held by syz.2.4451/17730: #0: ffffffff9012a3e8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline] #0: ffffffff9012a3e8 (rtnl_mutex){+.+.}-{4:4}, at: rtnetlink_rcv_msg+0x371/0xe90 net/core/rtnetlink.c:6961

stack backtrace: CPU: 1 UID: 0 PID: 17730 Comm: syz.2.4451 Not tainted 6.15.0-rc7-syzkaller-00082-g5cdb2c77c4c3 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:120 lockdep_rcu_suspicious+0x166/0x260 kernel/locking/lockdep.c:6865 mpls_route_input_rcu+0x1d4/0x200 net/mpls/af_mpls.c:84 mpls_getroute+0x621/0x1ea0 net/mpls/af_mpls.c:2381 rtnetlink_rcv_msg+0x3c9/0xe90 net/core/rtnetlink.c:6964 netlink_rcv_skb+0x16d/0x440 net/netlink/af_netlink.c:2534 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x53a/0x7f0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg net/socket.c:727 [inline] ____sys_sendmsg+0xa98/0xc70 net/socket.c:2566 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620 __sys_sendmmsg+0x200/0x420 net/socket.c:2709 __do_sys_sendmmsg net/socket.c:2736 [inline] __se_sys_sendmmsg net/socket.c:2733 [inline] __x64_sys_sendmmsg+0x9c/0x100 net/socket.c:2733 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f0a2818e969 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f0a28f52038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f0a283b5fa0 RCX: 00007f0a2818e969 RDX: 0000000000000003 RSI: 0000200000000080 RDI: 0000000000000003 RBP: 00007f0a28210ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f0a283b5fa0 R15: 00007ffce5e9f268 </TASK>

Which versions are affected by CVE-2025-38324?

It affects 2 products.

Products include Debian Debian Linux, Linux kernel.

How do I fix CVE-2025-38324?

Apply the vendor's patch.

Is CVE-2025-38324 being exploited?

There is no known exploitation of CVE-2025-38324 in the wild and no public exploit code.

All Debian Debian Linux vulnerabilities

Sources

Also known as AZL-64953, BELL-CVE-2025-38324, DEBIAN-CVE-2025-38324, GHSA-94vx-8jmh-wjcj, ROOT-OS-DEBIAN-11-CVE-2025-38324, ROOT-OS-DEBIAN-12-CVE-2025-38324 and 3 more.