[CVE-2026-74283][IMPORTANT] tipc: require net admin for TIPCv2 netlink mutators [ Upstream

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

CVE: CVE-2026-74283
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: tipc: require net admin for TIPCv2 netlink mutators [ Upstream
Commit: b06fb5f78a9af0929aaa47c92d0b7bca0617fb25
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b06fb5f78a9af0929aaa47c92d0b7bca0617fb25
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74283
Analysis date: Sun, 16 Aug 2026 08:17:32 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
TIPCv2 generic netlink mutators lacked the required CAP_NET_ADMIN gate, allowing a local unprivileged process to modify TIPC network identity, bearer state, and key material, causing integrity and availability impact with possible confidentiality concerns in secured TIPC deployments.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74283 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74283

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: IMPORTANT
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
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CVE-2026-74283	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-862;CWE-284;CWE-269;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H';BEST CVSS score: '7.8';DESCR 'TIPCv2 generic netlink mutators were registered without an administrative permission gate, allowing a local unprivileged process to change TIPC state through commands such as TIPC_NL_NET_SET, TIPC_NL_KEY_SET, TIPC_NL_KEY_FLUSH, and bearer enable or disable. For the CVSS the PR:L is used because a local user or process with no capabilities can trigger the vulnerable generic netlink operations, while no CAP_NET_ADMIN or root access is required. The issue is not directly network reachable because the vulnerable entry point is a local generic netlink control interface, but the consequences affect network-facing TIPC behavior. Impact includes unauthorized modification of TIPC network identity, bearer state, link settings, monitor settings, and key material. This can break cluster communication, disable or enable bearers, flush encryption keys, and weaken the integrity and availability of the TIPC configuration.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	KASAN TIPC IMPROVEONLY LINUS 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. The commit explicitly says uid/gid 65534 with zero effective capabilities could change TIPC state.
* Security-boundary bypass with practical sensitive-object access: +2. The bug bypasses the intended CAP_NET_ADMIN gate for administrative TIPC operations.
* Practical exploit chain demonstrated or strongly implied: +1. The repro successfully changed network id, node identity, key material, and UDP bearer state.
* Integrity impact plausible: +1. An unprivileged user can modify TIPC configuration and key state.
* Availability impact realistic: +1. Disabling bearers or flushing keys can break TIPC communication.
* Rare AND difficult-to-reach subsystem/configuration: -1. TIPC is not a universal default workload and usually matters only where TIPC is enabled or loaded.

Paranoid additional signals:

* Confidentiality impact plausible: +1. Unauthorized manipulation of TIPC key material can weaken or disrupt expected secure communication semantics.
* Cross-boundary isolation/policy bypass: +1. The issue bypasses a namespace-aware network administration capability boundary.

No memory corruption signals are applied. This is an authorization bypass, not UAF, OOB, double free, or type confusion.

## 3. Reachability analysis

The vulnerable entry point is local generic netlink. A local unprivileged process can trigger it without CAP_NET_ADMIN before the patch. It is not directly network-triggerable by packets, but the consequences affect network-facing TIPC state, including bearer enable or disable and key operations.

Namespaces matter because the fix uses GENL_UNS_ADMIN_PERM, matching namespace-aware CAP_NET_ADMIN behavior. Before the patch, even a process with no capabilities could perform operations that should require network administration privileges. Practical exposure depends on whether TIPC is enabled or the module is loaded, so the subsystem is not as broadly exposed as core TCP/IP or netfilter packet paths.

## 4. Severity interpretation

This behaves more like an actionable Moderate or Important candidate than an ordinary Moderate. There is no demonstrated kernel memory corruption or direct LPE primitive. However, the bug is a clear local capability bypass with demonstrated modification of sensitive networking state and key material.

The conservative score lands in Actionable Moderate because the issue is local and TIPC-dependent. The paranoid score reaches Strong Important candidate because the affected operations cross an intended CAP_NET_ADMIN boundary and can alter key material and network identity without privileges.

## 5. One-sentence report phrase

TIPCv2 generic netlink mutators lacked the required CAP_NET_ADMIN gate, allowing a local unprivileged process to modify TIPC network identity, bearer state, and key material, causing integrity and availability impact with possible confidentiality concerns in secured TIPC deployments.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a demonstrated local authorization bypass of administrative networking controls, not a low-risk crash-only bug. The impact depends on TIPC deployment and key usage, but it should not be auto-closed.

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

Patch: tipc: require net admin for TIPCv2 netlink mutators [ Upstream
Commit: b06fb5f78a9af0929aaa47c92d0b7bca0617fb25
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b06fb5f78a9af0929aaa47c92d0b7bca0617fb25

Changed files:
  net/tipc/netlink.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=b06fb5f78a9af0929aaa47c92d0b7bca0617fb25

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

The original Linux kernel CVE announcement for CVE-2026-74283 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74283

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:L/PR:L/UI:N/S:U/C:L/I:H/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 5
  Paranoid ActionableScore: 7

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

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).