[CVE-2026-52945][MODERATE 7.0] Revert "wireguard: device: enable threaded NAPI" This reverts commit 933466f which is

[CVE-2026-52945][MODERATE 7.0] Revert "wireguard: device: enable threaded NAPI" This reverts commit 933466f which is

[AL-KERNEL]

CVE: CVE-2026-52945
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Revert "wireguard: device: enable threaded NAPI" This reverts commit 933466f which is
Commit: e94b369ff82f9bc84f090f271bd78f41c9f6ab2f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e94b369ff82f9bc84f090f271bd78f41c9f6ab2f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52945
Analysis date: Wed, 24 Jun 2026 15:50:12 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A WireGuard threaded NAPI regression can permanently stall RX decryption for a peer under heavy network load, causing persistent peer-level traffic loss in affected WireGuard or Cilium deployments without evidence of memory corruption or privilege escalation.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-52945 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52945

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: MODERATE 7.0
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-52945	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-400;CWE-667;*CWE-833;Other CVSS 'AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.9';DESCR 'WireGuard RX processing can permanently stall for a single peer when threaded NAPI is enabled and packet decryption completion is observed out of order under heavy network load. The peer rx_queue can fill up to MAX_QUEUED_PACKETS and new packets for that peer are then dropped, while other peers and the host may continue to look healthy. For the CVSS the PR:N is used in the paranoid score because a remote peer or traffic source may trigger the condition without local privileges on the target system. The base score uses PR:L because reliable triggering usually requires access to configured WireGuard peer traffic or an internal Cilium Kubernetes network using WireGuard encryption. The issue is network reachable in affected deployments, but it is a denial of service only and there is no supported memory corruption or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	READ BPF LEAK NETWORK SKB KERNEL_PANIC_PLUS_UAF HARDWARE PACKET  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative score:

* +2 Remote reachable / network-triggerable: the affected path is WireGuard RX processing and can be influenced by peer traffic in deployed WireGuard or Cilium Kubernetes encryption setups.
* +1 Reliable kernel crash / strong DoS equivalent: no crash occurs, but RX decryption for the affected peer can permanently stall and new packets for that peer are dropped.
* +1 Availability impact realistic: the stall is persistent for the affected peer and does not self-recover.
* +1 Broad/default/common subsystem or broadly deployed exposure: WireGuard is a commonly deployed kernel VPN path, especially in Kubernetes Cilium environments.
* -1 Hard or unreliable race / special timing required: the issue occurs rarely and requires heavy networking load plus an ordering corner case in threaded NAPI scheduling.

Paranoid score difference:

* The paranoid score does not subtract the hard-race point because multiple independent production reports show that the condition is realistic under heavy load.

No memory-corruption, UAF, OOB write, privilege-escalation, confidentiality, or integrity signals are supported by the patch.

## 3. Reachability analysis

The bug can be triggered by traffic reaching an affected WireGuard peer when threaded NAPI is enabled by the backported change. In practice, this most likely requires access to a configured WireGuard peer relationship or to an internal Cilium Kubernetes network using WireGuard for east-west encryption. It is not a generic unauthenticated Internet packet parsing bug for arbitrary hosts, but it is network-reachable in affected deployments. Namespaces and containers matter mainly because Cilium and Kubernetes deployments may expose this path through pod or node traffic, but the bug does not require local code execution on the target node.

## 4. Severity interpretation

This behaves like an actionable Moderate network DoS, not an Important memory-corruption issue. The realistic impact is persistent loss of RX processing for a specific WireGuard peer, while other peers and the host may continue operating normally. There is no evidence of attacker-controlled memory corruption, object lifetime misuse, privilege escalation, information disclosure, or integrity impact. The issue should not be auto-closed as low-risk because it is production-observed, network-triggerable in real deployments, and persistent once triggered.

## 5. One-sentence report phrase

A WireGuard threaded NAPI regression can permanently stall RX decryption for a peer under heavy network load, causing persistent peer-level traffic loss in affected WireGuard or Cilium deployments without evidence of memory corruption or privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Network-reachable persistent DoS in a real production deployment class should be reviewed manually, even though the bug is DoS-only and does not currently support Important-class memory-corruption treatment.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: Revert "wireguard: device: enable threaded NAPI" This reverts commit 933466f which is
Commit: e94b369ff82f9bc84f090f271bd78f41c9f6ab2f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e94b369ff82f9bc84f090f271bd78f41c9f6ab2f

Commit description:

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:

  1) skbs arriving for decryption are enqueued to the peer->rx_queue in
     wg_packet_consume_data via wg_queue_enqueue_per_device_and_peer.
  2) 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.
  3) 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.
  4) 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.
  5) The latter updates the state to PACKET_STATE_CRYPTED on success
     and calls napi_schedule on the per peer->napi instance.
  6) 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.)
  7) 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.
  8) 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.
  9) While this is the case, the other CPUs in the meantime finish
     decryption and call into napi_schedule.
 10) 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 early
     with work_done = 0 and calls napi_complete_done, signalling
     it "finished" processing.
 11) The assumption in wg_packet_decrypt_worker is that when the
     decryption finished the subsequent napi_schedule will always
     lead to a later invocation of wg_packet_rx_poll to pick up
     the finished packet.
 12) However, it appears that a later napi_schedule does /not/
     schedule a later poll and thus no wg_packet_rx_poll.
 13) If this situation happens exactly for the corner case where
     the decryption worker of the first packet is stuck and waiting
     to be scheduled, and the network load for WireGuard is very
     high then the queue can build up to MAX_QUEUED_PACKETS.
 14) If this situation occurs, then no new decryption worker will
     be scheduled and also no new napi_schedule to make forward
     progress.
 15) This means the peer->rx_queue stops processing packets completely

[Commit description truncated; see the upstream URL below]

Changed files:
  drivers/net/wireguard/device.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e94b369ff82f9bc84f090f271bd78f41c9f6ab2f

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-52945 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52945

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.9

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 4
  Paranoid ActionableScore: 5

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).