[CVE-2026-45901][LOW] netfilter: nf_tables: revert commit_mutex usage in reset path [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-45901
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: netfilter: nf_tables: revert commit_mutex usage in reset path [ Upstream
Commit: ee3978b6a0dcd4215cb7cedcba705a12174786a7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee3978b6a0dcd4215cb7cedcba705a12174786a7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45901
Analysis date: Wed, 27 May 2026 22:21:22 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A nf_tables reset locking bug can deadlock with ipset and netlink callback locks during concurrent firewall control-plane operations, causing local firewall management DoS.

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

The original Linux kernel CVE announcement for CVE-2026-45901 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45901

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: YES

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

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

CVE-2026-45901	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-667;*CWE-833;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'nf_tables reset operations could take commit_mutex in paths that interact with ipset and netlink dump callbacks, creating a circular lock dependency between commit_mutex, nfnl_subsys_ipset, and nlk_cb_mutex. A local actor with nftables and ipset configuration rights could trigger a deadlock by running nft reset, ipset list, and iptables-nft set matching operations concurrently. For the CVSS the PR:L is used in the paranoid score because delegated CAP_NET_ADMIN in containers or service accounts can expose these control plane operations below full host root, while typical host triggering requires network administration privileges. The issue is not network reachable and is triggered through netfilter configuration operations rather than packet traffic. Impact is denial of service through stuck netfilter or netlink control plane operations. No supported evidence indicates information disclosure, integrity impact, kernel memory corruption, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 2) 	MAYBE	REMOTE LOCK DANGER INIT NETFILTER SKB LOG LINUS SYZBOT  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

* Reliable kernel/control-plane DoS: +1
  The bug can create a circular lock dependency and deadlock nf_tables/ipset/netlink control-plane operations.

* Availability impact realistic: +1
  A deadlock can leave nftables reset, ipset list, or iptables-nft operations stuck, affecting firewall management.

* Broad/common subsystem: +1 in paranoid scoring
  nf_tables, ipset compatibility, and iptables-nft are common firewall/control-plane components.

* Local delegated network administration trigger: +1 in paranoid scoring
  In containers, namespaces, appliances, or managed services, CAP_NET_ADMIN-like firewall control may be delegated below full host root.

* Requires CAP_NET_ADMIN in typical deployments: -2 conservative
  Normal triggering requires nftables/ipset/iptables-nft configuration rights.

* Concurrent/special operation mix required: -1
  The issue requires overlapping nft reset, ipset list, and iptables-nft set matching operations.

* No memory corruption: +0
  This is a locking/order bug, not UAF, OOB write, arbitrary write, or object lifetime corruption.

* No direct network reachability: +0
  The trigger is local netfilter configuration activity, not packet traffic.

## 3. Reachability analysis

A local actor with nftables and ipset administration rights can trigger the issue by running the affected reset and listing operations concurrently with iptables-nft set matching. In normal host deployments this requires CAP_NET_ADMIN. Namespaces and containers can lower the practical barrier if network administration is delegated to tenants or service accounts.

The issue is not remotely packet-triggerable. Traffic may exist in the environment, but the vulnerable path is netlink/control-plane locking.

## 4. Severity interpretation

This behaves like ordinary Moderate or borderline Moderate availability impact. It is operationally relevant because nf_tables is common and firewall management may hang, but it is not memory corruption, not privilege escalation, and not a remote network parsing flaw. The paranoid score is higher only for deployments that delegate firewall administration to less trusted users.

## 5. One-sentence report phrase

A nf_tables reset locking bug can deadlock with ipset and netlink callback locks during concurrent firewall control-plane operations, causing local firewall management DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

No manual check is needed for standard deployments where nftables and ipset management requires trusted CAP_NET_ADMIN. Review only if delegated firewall administration is exposed to untrusted tenants or service accounts.

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

Patch: netfilter: nf_tables: revert commit_mutex usage in reset path [ Upstream
Commit: ee3978b6a0dcd4215cb7cedcba705a12174786a7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee3978b6a0dcd4215cb7cedcba705a12174786a7

Changed files:
  net/netfilter/nf_tables_api.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=ee3978b6a0dcd4215cb7cedcba705a12174786a7

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

The original Linux kernel CVE announcement for CVE-2026-45901 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45901

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:H
  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: 1
  Paranoid ActionableScore: 3

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).