[CVE-2026-46266][MODERATE 7.0] inet: RAW sockets using IPPROTO_RAW MUST drop incoming ICMP [ Upstream

[CVE-2026-46266][MODERATE 7.0] inet: RAW sockets using IPPROTO_RAW MUST drop incoming ICMP [ Upstream

[AL-KERNEL]

CVE: CVE-2026-46266
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: inet: RAW sockets using IPPROTO_RAW MUST drop incoming ICMP [ Upstream
Commit: db76b75ede3810e7cf9cfea5067d4f3e0993768b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=db76b75ede3810e7cf9cfea5067d4f3e0993768b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46266
Analysis date: Wed, 03 Jun 2026 15:38:00 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
Incoming ICMP or ICMPv6 errors with an embedded IPPROTO_RAW protocol value could be incorrectly delivered to local IPPROTO_RAW raw sockets, allowing a remote sender to influence FNHE route cache state and potentially cause network denial of service when such a socket exists.

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

The original Linux kernel CVE announcement for CVE-2026-46266 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46266

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-2026-46266	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:L/A:H';*CWE-20;CWE-345;CWE-693;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '6.5';DESCR 'Incoming ICMP or ICMPv6 error processing could incorrectly treat an embedded protocol value of IPPROTO_RAW as deliverable to a local raw socket. A remote attacker can send a crafted ICMP error with an inner IP header using protocol 255 and may cause FNHE route cache changes, such as route exception or PMTU state changes, when a matching IPPROTO_RAW socket exists on the target. For the CVSS the PR:N is used because the remote sender does not need privileges on the victim host, although reliable triggering depends on a local process having created an IPPROTO_RAW raw socket. The issue is network reachable but has an important environmental precondition, so AC:H is used. Impact is mainly denial of service and low integrity impact through route cache manipulation, not memory corruption or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 6) 	MAYBE	REMOTE NETWORK SKB IPV6 KPANIC PACKET 	-	-	checked

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

ActionableScore=6
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative score 5:

* Remote reachable / network-triggerable: +2
  Crafted incoming ICMP or ICMPv6 error packets can reach the affected path remotely.
* Common networking core path or packet-processing path: +1
  The bug is in IPv4/IPv6 ICMP error handling and raw socket delivery.
* Integrity impact plausible: +1
  The attacker can influence FNHE route cache state, such as route exception or PMTU behavior.
* Availability impact realistic: +1
  Incorrect FNHE or PMTU cache changes can degrade or disrupt connectivity.

Paranoid score adds:

* Broad/default/common subsystem exposure: +1
  ICMP handling is part of the default IP stack, even though the trigger depends on a matching local IPPROTO_RAW socket.

Not counted:

* No generic memory corruption.
* No UAF, OOB write, double-free, or refcount lifetime bug.
* No plausible privilege escalation from the patch context.
* No reliable kernel crash is shown.

## 3. Reachability analysis

A remote attacker can send crafted ICMP or ICMPv6 error packets, but practical triggering depends on the target already having a local raw socket using IPPROTO_RAW. Creating such a socket usually requires CAP_NET_RAW, but that privilege is needed by the local socket creator, not by the remote sender. Containers or delegated network capabilities may make the environmental precondition more common, but the attack itself remains network-originated once the socket exists. The path is in common ICMP processing, but the specific vulnerable behavior requires the unusual IPPROTO_RAW raw socket condition.

## 4. Severity interpretation

This behaves like an actionable Moderate networking issue, not an Important memory-corruption issue. The realistic impact is remote route-cache or PMTU-state manipulation that may cause connectivity degradation or denial of service. The theoretical risk does not extend to privilege escalation or arbitrary memory corruption based on this patch. The paranoid score is higher because the affected path is network reachable and touches core routing exception state.

## 5. One-sentence report phrase

Incoming ICMP or ICMPv6 errors with an embedded IPPROTO_RAW protocol value could be incorrectly delivered to local IPPROTO_RAW raw sockets, allowing a remote sender to influence FNHE route cache state and potentially cause network denial of service when such a socket exists.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the issue is network reachable and can remotely influence routing exception cache state under a specific local socket precondition, so it should not be auto-closed even though there is no evidence of memory corruption or privilege escalation.

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

Patch: inet: RAW sockets using IPPROTO_RAW MUST drop incoming ICMP [ Upstream
Commit: db76b75ede3810e7cf9cfea5067d4f3e0993768b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=db76b75ede3810e7cf9cfea5067d4f3e0993768b

Changed files:
  net/ipv4/icmp.c
  net/ipv6/icmp.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=db76b75ede3810e7cf9cfea5067d4f3e0993768b

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

The original Linux kernel CVE announcement for CVE-2026-46266 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46266

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:N/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
  The Best / paranoid CVSS score: 6.5

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: 6

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).