[CVE-2026-45917][LOW] ipvs: do not keep dest_dst if dev is going down [ Upstream

[CVE-2026-45917][LOW] ipvs: do not keep dest_dst if dev is going down [ Upstream

[AL-KERNEL]

CVE: CVE-2026-45917
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ipvs: do not keep dest_dst if dev is going down [ Upstream
Commit: 64af43033503458c46023e56d6ae7bb0f824b55f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=64af43033503458c46023e56d6ae7bb0f824b55f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45917
Analysis date: Wed, 27 May 2026 21:31:43 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
An IPVS dst cache race during netdev teardown can attach a cached route to a device that is going down, leaking a `net_device` reference and causing local availability or cleanup impact.

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

The original Linux kernel CVE announcement for CVE-2026-45917 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45917

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: LOW
Manual review required: NO

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

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

CVE-2026-45917	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'An IPVS dst cache race can attach a new dest_dst to a route whose net_device is already going down, after the netdev notifier has dropped the old cached dst. This can leak a device reference until the IPVS destination is removed and may interfere with device teardown or network service cleanup. For the CVSS the PR:L is used in the paranoid score because delegated network administration in containers or service accounts can make IPVS and netdev control reachable below full host root, while typical reliable triggering requires CAP_NET_ADMIN. The issue is not directly network reachable, although packet traffic may help exercise the route lookup path during local device teardown. Impact is availability only through leaked references or stuck network cleanup, with no supported evidence of information disclosure, integrity impact, kernel memory corruption, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) 	MAYBE	REMOTE INIT NETFILTER RACE LEAK HARDWARE LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

* Local trigger with delegated network administration: +1 in paranoid scoring
  A less privileged service or container with delegated IPVS or netdev management could potentially exercise the race below full host root.

* Availability impact realistic: +1
  The impact is a leaked `net_device` reference that may delay or block device teardown or IPVS cleanup.

* Hard race or special timing required: -1
  The bug requires a race between `ip_vs_dst_event()` during device teardown and route lookup or dst caching.

* Requires CAP_NET_ADMIN in typical deployments: -2 conservative
  Reliable triggering normally requires IPVS configuration control and network device teardown, which are privileged operations.

* No generic memory corruption: +0
  This is a reference leak / dst cache race, not UAF, double-free, OOB write, arbitrary write, or heap corruption.

* No direct network reachability: +0
  Packet traffic may exercise the lookup path, but the critical condition is local device shutdown and cache replacement.

## 3. Reachability analysis

The issue is reachable in IPVS configurations during network device teardown while route lookup can still return a route for a device that is going down. In normal deployments, controlling IPVS destinations and bringing devices down requires `CAP_NET_ADMIN`. Containers or namespaces may lower practical privilege if network administration is delegated, but this is still a local control-plane race.

It is not directly remotely triggerable by packets alone. Realistic exploitation is limited to resource leak or stuck cleanup behavior.

## 4. Severity interpretation

This behaves like ordinary Moderate or Low-like DoS. The realistic impact is leaked device references and possible network cleanup interference. The patch does not support memory corruption, privilege escalation, information disclosure, or a strong cross-boundary primitive.

## 5. One-sentence report phrase

An IPVS dst cache race during netdev teardown can attach a cached route to a device that is going down, leaking a `net_device` reference and causing local availability or cleanup impact.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

The issue is a local privileged or delegated-network-admin race causing a reference leak, with no demonstrated memory corruption, remote trigger, or privilege escalation path.

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

Patch: ipvs: do not keep dest_dst if dev is going down [ Upstream
Commit: 64af43033503458c46023e56d6ae7bb0f824b55f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=64af43033503458c46023e56d6ae7bb0f824b55f

Changed files:
  net/netfilter/ipvs/ip_vs_xmit.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=64af43033503458c46023e56d6ae7bb0f824b55f

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

The original Linux kernel CVE announcement for CVE-2026-45917 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45917

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:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 0
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).