CVE-2026-52945High· 7.5▾ Twilight

In the Linux kernel, the following vulnerability has been resolved: Revert "wireguard: device: enable threaded NAPI" This reverts commit 933466fc50a8e4eb167acbd0d8ec96a078462e9c which is commit db9ae3b6b43c79b1ba87eea849fd65efa05b4b2e …

▾ Twilight zone — High severity, or a signal on a lesser flaw

Depth score41/ 100 · Moderate

impact 41.3 · likelihood 0.1 · exploitation 0

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Proof of concept

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Published

Jun 24, 2026

Updated

Jul 10, 2026

CVSS

7.5

Vendor

Red Hat

Product

Red Hat Enterprise Linux 9

CWE

CWE-367

Depth score

41 · Moderate

EPSS

0.32% · p24

Platforms

—

Source

NVD

Vector

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

Scores by source

NVD 7.5 · CNA 7.5 · Vendor 7.0

CISA SSVC

decided 2026-10-16

Exploitation: none
Automatable: yes
Technical impact: partial

Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.

EPSS history

Exploit-prediction probability, daily snapshots since Jul 29.

0.3% → 0.3%

Timeline

Disclosure to exploitation, from the record and what we observed since indexing it.

4 events · 61 days

Jun 24, 2026Published
Disclosed via NVD
Jul 10, 2026Record revised
Last analysed / modified upstream
Jul 29, 2026EPSS first tracked
0.3%
Aug 24, 2026EPSS peak
0.3% → 0.4%

Red Hat CWE-367 #nvd #csaf #vex #red-hat #cve.org

Affected

enterprise_linux 10
enterprise_linux 9

Full technical detail▾

Overview

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

Revert "wireguard: device: enable threaded NAPI"

This reverts commit 933466fc50a8e4eb167acbd0d8ec96a078462e9c which is commit db9ae3b6b43c79b1ba87eea849fd65efa05b4b2e upstream.

We have had three independent production user reports in combination with Cilium utilizing WireGuard as encryption underneath that k8s Pod E/W traffic to certain peer nodes fully stalled. The situation appears as follows:

Occurs very rarely but at random times under heavy networking load.
Once the issue triggers the decryption side stops working completely for that WireGuard peer, other peers keep working fine. The stall happens also for newly initiated connections towards that particular WireGuard peer.
Only the decryption side is affected, never the encryption side.
Once it triggers, it never recovers and remains in this state, the CPU/mem on that node looks normal, no leak, busy loop or crash.
bpftrace on the affected system shows that wg_prev_queue_enqueue fails, thus the MAX_QUEUED_PACKETS (1024 skbs!) for the peer's rx_queue is reached.
Also, bpftrace shows that wg_packet_rx_poll for that peer is never called again after reaching this state for that peer. For other peers wg_packet_rx_poll does get called normally.
Commit db9ae3b ("wireguard: device: enable threaded NAPI") switched WireGuard to threaded NAPI by default. The default has not been changed for triggering the issue, neither did CPU hotplugging occur (i.e. 5bd8de2 ("wireguard: queueing: always return valid online CPU in wg_cpumask_choose_online()")).
The issue has been observed with stable kernels of v5.15 as well as v6.1. It was reported to us that v5.10 stable is working fine, and no report on v6.6 stable either (somewhat related discussion in [0] though).
In the WireGuard driver the only material difference between v5.10 stable and v5.15 stable is the switch to threaded NAPI by default.

[0] https://lore.kernel.org/netdev/CA+wXwBTT74RErDGAnj98PqS=wvdh8eM1pi4q6tTdExtjnokKqA@mail.gmail.com/

Breakdown of the problem:

skbs arriving for decryption are enqueued to the peer->rx_queue in wg_packet_consume_data via wg_queue_enqueue_per_device_and_peer.
The latter only moves the skb into the MPSC peer queue if it does not surpass MAX_QUEUED_PACKETS (1024) which is kept track in an atomic counter via wg_prev_queue_enqueue.
In case enqueueing was successful, the skb is also queued up in the device queue, round-robin picks a next online CPU, and schedules the decryption worker.
The wg_packet_decrypt_worker, once scheduled, picks these up from the queue, decrypts the packets and once done calls into wg_queue_enqueue_per_peer_rx.
The latter updates the state to PACKET_STATE_CRYPTED on success and calls napi_schedule on the per peer->napi instance.
NAPI then polls via wg_packet_rx_poll. wg_prev_queue_peek checks on the peer->rx_queue. It will wg_prev_queue_dequeue if the queue->peeked skb was not cached yet, or just return the latter otherwise. (wg_prev_queue_drop_peeked later clears the cache.)
From an ordering perspective, the peer->rx_queue has skbs in order while the device queue with the per-CPU worker threads from a global ordering PoV can finish the decryption and signal the skb PACKET_STATE_CRYPTED out of order.
A situation can be observed that the first packet coming in will be stuck waiting for the decryption worker to be scheduled for a longer time when the system is under pressure.
While this is the case, the other CPUs in the meantime finish decryption and call into napi_schedule.
Now in wg_packet_rx_poll it picks up the first in-order skb from the peer->rx_queue and sees that its state is still PACKET_STATE_UNCRYPTED. The NAPI poll routine then exits e ---truncated---

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

Red Hat VEX · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-10-02 · vex

References

Related vulnerabilities

Connected by shared product, vendor, weakness, or advisory.

#nvd#csaf#vex#red-hat#cve.org

▾ Twilight zone — High severity, or a signal on a lesser flaw

Depth score41/ 100 · Moderate

impact 41.3 · likelihood 0.1 · exploitation 0

Overview

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

Revert "wireguard: device: enable threaded NAPI"

This reverts commit 933466fc50a8e4eb167acbd0d8ec96a078462e9c which is commit db9ae3b6b43c79b1ba87eea849fd65efa05b4b2e upstream.

Occurs very rarely but at random times under heavy networking load.

Once the issue triggers the decryption side stops working completely for that WireGuard peer, other peers keep working fine. The stall happens also for newly initiated connections towards that particular WireGuard peer.

Only the decryption side is affected, never the encryption side.

Once it triggers, it never recovers and remains in this state, the CPU/mem on that node looks normal, no leak, busy loop or crash.

bpftrace on the affected system shows that wg_prev_queue_enqueue fails, thus the MAX_QUEUED_PACKETS (1024 skbs!) for the peer's rx_queue is reached.

Also, bpftrace shows that wg_packet_rx_poll for that peer is never called again after reaching this state for that peer. For other peers wg_packet_rx_poll does get called normally.

Commit db9ae3b ("wireguard: device: enable threaded NAPI") switched WireGuard to threaded NAPI by default. The default has not been changed for triggering the issue, neither did CPU hotplugging occur (i.e. 5bd8de2 ("wireguard: queueing: always return valid online CPU in wg_cpumask_choose_online()")).

The issue has been observed with stable kernels of v5.15 as well as v6.1. It was reported to us that v5.10 stable is working fine, and no report on v6.6 stable either (somewhat related discussion in [0] though).

In the WireGuard driver the only material difference between v5.10 stable and v5.15 stable is the switch to threaded NAPI by default.

[0] https://lore.kernel.org/netdev/CA+wXwBTT74RErDGAnj98PqS=wvdh8eM1pi4q6tTdExtjnokKqA@mail.gmail.com/

Breakdown of the problem:

skbs arriving for decryption are enqueued to the peer->rx_queue in wg_packet_consume_data via wg_queue_enqueue_per_device_and_peer.

The latter only moves the skb into the MPSC peer queue if it does not surpass MAX_QUEUED_PACKETS (1024) which is kept track in an atomic counter via wg_prev_queue_enqueue.

In case enqueueing was successful, the skb is also queued up in the device queue, round-robin picks a next online CPU, and schedules the decryption worker.

The wg_packet_decrypt_worker, once scheduled, picks these up from the queue, decrypts the packets and once done calls into wg_queue_enqueue_per_peer_rx.

The latter updates the state to PACKET_STATE_CRYPTED on success and calls napi_schedule on the per peer->napi instance.

NAPI then polls via wg_packet_rx_poll. wg_prev_queue_peek checks on the peer->rx_queue. It will wg_prev_queue_dequeue if the queue->peeked skb was not cached yet, or just return the latter otherwise. (wg_prev_queue_drop_peeked later clears the cache.)

From an ordering perspective, the peer->rx_queue has skbs in order while the device queue with the per-CPU worker threads from a global ordering PoV can finish the decryption and signal the skb PACKET_STATE_CRYPTED out of order.

A situation can be observed that the first packet coming in will be stuck waiting for the decryption worker to be scheduled for a longer time when the system is under pressure.

While this is the case, the other CPUs in the meantime finish decryption and call into napi_schedule.

Now in wg_packet_rx_poll it picks up the first in-order skb from the peer->rx_queue and sees that its state is still PACKET_STATE_UNCRYPTED. The NAPI poll routine then exits e ---truncated---