CVE-2026-23173 in Linux
Summary
by MITRE • 02/14/2026
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5e: TC, delete flows only for existing peers
When deleting TC steering flows, iterate only over actual devcom peers instead of assuming all possible ports exist. This avoids touching non-existent peers and ensures cleanup is limited to devices the driver is currently connected to.
BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 133c8a067 P4D 0 Oops: Oops: 0002 [#1] SMP
CPU: 19 UID: 0 PID: 2169 Comm: tc Not tainted 6.18.0+ #156 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 RIP: 0010:mlx5e_tc_del_fdb_peers_flow+0xbe/0x200 [mlx5_core]
Code: 00 00 a8 08 74 a8 49 8b 46 18 f6 c4 02 74 9f 4c 8d bf a0 12 00 00 4c 89 ff e8 0e e7 96 e1 49 8b 44 24 08 49 8b 0c 24 4c 89 ff <48> 89 41 08 48 89 08 49 89 2c 24 49 89 5c 24 08 e8 7d ce 96 e1 49 RSP: 0018:ff11000143867528 EFLAGS: 00010246 RAX: 0000000000000000 RBX: dead000000000122 RCX: 0000000000000000 RDX: ff11000143691580 RSI: ff110001026e5000 RDI: ff11000106f3d2a0 RBP: dead000000000100 R08: 00000000000003fd R09: 0000000000000002 R10: ff11000101c75690 R11: ff1100085faea178 R12: ff11000115f0ae78 R13: 0000000000000000 R14: ff11000115f0a800 R15: ff11000106f3d2a0 FS: 00007f35236bf740(0000) GS:ff110008dc809000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000008 CR3: 0000000157a01001 CR4: 0000000000373eb0 Call Trace: <TASK> mlx5e_tc_del_flow+0x46/0x270 [mlx5_core]
mlx5e_flow_put+0x25/0x50 [mlx5_core]
mlx5e_delete_flower+0x2a6/0x3e0 [mlx5_core]
tc_setup_cb_reoffload+0x20/0x80 fl_reoffload+0x26f/0x2f0 [cls_flower]
? mlx5e_tc_reoffload_flows_work+0xc0/0xc0 [mlx5_core]
? mlx5e_tc_reoffload_flows_work+0xc0/0xc0 [mlx5_core]
tcf_block_playback_offloads+0x9e/0x1c0 tcf_block_unbind+0x7b/0xd0 tcf_block_setup+0x186/0x1d0 tcf_block_offload_cmd.isra.0+0xef/0x130 tcf_block_offload_unbind+0x43/0x70 __tcf_block_put+0x85/0x160 ingress_destroy+0x32/0x110 [sch_ingress]
__qdisc_destroy+0x44/0x100 qdisc_graft+0x22b/0x610 tc_get_qdisc+0x183/0x4d0 rtnetlink_rcv_msg+0x2d7/0x3d0 ? rtnl_calcit.isra.0+0x100/0x100 netlink_rcv_skb+0x53/0x100 netlink_unicast+0x249/0x320 ? __alloc_skb+0x102/0x1f0 netlink_sendmsg+0x1e3/0x420 __sock_sendmsg+0x38/0x60 ____sys_sendmsg+0x1ef/0x230 ? copy_msghdr_from_user+0x6c/0xa0 ___sys_sendmsg+0x7f/0xc0 ? ___sys_recvmsg+0x8a/0xc0 ? __sys_sendto+0x119/0x180 __sys_sendmsg+0x61/0xb0 do_syscall_64+0x55/0x640 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f35238bb764 Code: 15 b9 86 0c 00 f7 d8 64 89 02 b8 ff ff ff ff eb bf 0f 1f 44 00 00 f3 0f 1e fa 80 3d e5 08 0d 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 4c c3 0f 1f 00 55 48 89 e5 48 83 ec 20 89 55 RSP: 002b:00007ffed4c35638 EFLAGS: 00000202 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000055a2efcc75e0 RCX: 00007f35238bb764 RDX: 0000000000000000 RSI: 00007ffed4c356a0 RDI: 0000000000000003 RBP: 00007ffed4c35710 R08: 0000000000000010 R09: 00007f3523984b20 R10: 0000000000000004 R11: 0000000000000202 R12: 00007ffed4c35790 R13: 000000006947df8f R14: 000055a2efcc75e0 R15: 00007ffed4c35780
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Analysis
by VulDB Data Team • 05/05/2026
The vulnerability described in CVE-2026-23173 resides within the Linux kernel's mlx5e network driver, specifically in the handling of Traffic Control (TC) steering flows. This flaw manifests as a kernel NULL pointer dereference when attempting to delete TC steering flows, which occurs due to improper iteration over device communication (devcom) peers. The root cause lies in the assumption that all possible ports exist during flow deletion, leading to attempts to access non-existent peers and subsequently triggering a NULL pointer dereference at address 0x0000000000000008. The error code 0x0002 indicates a supervisor write access in kernel mode, which is a critical condition that can result in system crashes or potential privilege escalation.
The technical execution of this vulnerability involves the mlx5e_tc_del_fdb_peers_flow function within the mlx5_core driver module, where the driver iterates through all potential devcom peers without verifying their existence. This behavior leads to a kernel oops condition, as evidenced by the stack trace showing the call path from tc_setup_cb_reoffload through various TC subsystem functions to the final crash point. The kernel's memory management subsystem detects the invalid write operation to a NULL pointer, causing an immediate system failure. This issue directly maps to CWE-476, which describes NULL pointer dereference, and represents a classic case of improper resource management in kernel space.
The operational impact of this vulnerability is significant as it can lead to system instability and denial of service in environments using Mellanox mlx5 network adapters with TC steering enabled. The NULL pointer dereference can cause kernel panics, system crashes, and potentially allow attackers to exploit the vulnerability for privilege escalation or persistent denial of service attacks. The vulnerability affects systems running kernel versions that include the mlx5e driver with TC steering functionality, particularly those managing complex network topologies where devcom peers are dynamically configured or removed.
Mitigation strategies for this vulnerability include applying the latest kernel updates that contain the fix, which modifies the flow deletion logic to iterate only over actual devcom peers rather than assuming all possible ports exist. Administrators should also monitor network configurations to minimize the use of complex TC steering setups that could trigger the vulnerability. The fix aligns with ATT&CK technique T1068, which involves local privilege escalation through kernel vulnerabilities, by preventing the exploitation pathway that leads to kernel memory corruption. Additionally, implementing proper input validation and peer existence checks in kernel modules can prevent similar issues in other network drivers, following best practices for secure kernel programming and adhering to the principle of least privilege in kernel space operations.