[CVE-2026-53006][IMPORTANT] ipv6: fix possible UAF in icmpv6_rcv() [ Upstream

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

CVE: CVE-2026-53006
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: ipv6: fix possible UAF in icmpv6_rcv() [ Upstream
Commit: 7bff2c8fe5c35ae58bf73104f53db3676e6e5d94
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7bff2c8fe5c35ae58bf73104f53db3676e6e5d94
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53006
Analysis date: Thu, 25 Jun 2026 15:36:54 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A possible UAF read in icmpv6_rcv() occurs because IPv6 source and destination address pointers are cached before skb head may change, allowing remote ICMPv6 traffic to reach stale pointer debug logging paths and potentially cause limited information disclosure or kernel DoS.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-53006 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53006

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-2026-53006	IMPORTANT	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:L/I:N/A:H';*CWE-416;CWE-825;*CWE-664;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.5';DESCR 'An IPv6 ICMP receive path UAF can occur because icmpv6_rcv cached pointers to ipv6_hdr(skb) saddr and daddr before operations that may change skb head. If skb head is reallocated or replaced, later debug logging may dereference stale address pointers when reporting a checksum failure or an unknown ICMPv6 type. For the CVSS the PR:N is selected because a remote sender does not need privileges on the target when IPv6 ICMP input is reachable. The issue is network reachable via crafted ICMPv6 traffic, but practical triggering depends on skb layout changes and slow path debug logging, so AC:H is used. Impact is primarily denial of service through a UAF read and possible kernel crash. Limited confidentiality impact is possible if stale memory is formatted into logs, but no direct write primitive or privilege escalation is shown.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) 	MAYBE	REMOTE UAF NETWORK SKB IPV6 KPANIC 	-	-	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:

* Remote reachable / network-triggerable: +2. The affected code is in the IPv6 ICMP receive path and can be reached by incoming ICMPv6 packets.
* Memory corruption, weak/indirect corruption candidate: +1. The primitive is a stale pointer dereference/UAF read of cached IPv6 header address pointers, not an attacker-controlled write.
* Real lifetime corruption: +1. The issue is specifically that skb head may change after cached pointers were taken, leaving stale references.
* Common networking core path or packet-processing path: +1. ICMPv6 receive handling is a common packet-processing path.
* Special conditions / constrained trigger: -1. The dereference is in slow-path debug logging and depends on skb head movement plus an error/unknown-type path.

Paranoid additions/interpretation:

* Generic UAF memory corruption class: +2 instead of +1 weak corruption. The commit explicitly describes possible UAF due to skb head lifetime changes.
* Confidentiality impact plausible: +1. Stale memory may be formatted as IPv6 addresses into logs if the debug site is active.
* Availability impact realistic: +1. A stale pointer read in kernel networking code may crash under some memory/debug configurations, though no write primitive is shown.

No privilege escalation signal is counted. No integrity signal is counted. No arbitrary write, reclaim primitive, or controlled overwrite is demonstrated.

## 3. Reachability analysis

A remote host can potentially trigger the affected path by sending malformed or unusual ICMPv6 traffic that reaches icmpv6_rcv(). No local account is required if IPv6 input is reachable, so the practical PR interpretation is PR:N. The path is broadly present on IPv6-enabled systems, but practical exploitation depends on entering the checksum-failure or unknown-type debug path and on skb head movement after the original IPv6 header pointers were cached. Debug logging behavior may also affect whether the stale pointers are evaluated in a given build/runtime configuration.

Namespaces and containers are not required for the network trigger. They may affect exposure only indirectly through network namespace configuration, IPv6 enablement, firewalling, and whether ICMPv6 traffic can reach the host stack.

## 4. Severity interpretation

This behaves above an ordinary Moderate because it is a network-reachable UAF-read candidate in a common IPv6 packet-processing path. Realistic impact is most likely limited to DoS or limited stale-memory disclosure through logs. Theoretical memory corruption potential exists because the bug is a real stale pointer lifetime issue, but the patch does not show an attacker-controlled write primitive or a strong LPE path.

Conservative handling is Actionable Moderate. Paranoid handling reaches Strong Important candidate because early triage should not auto-close a remotely reachable UAF in core networking without manual review.

## 5. One-sentence report phrase

A possible UAF read in icmpv6_rcv() occurs because IPv6 source and destination address pointers are cached before skb head may change, allowing remote ICMPv6 traffic to reach stale pointer debug logging paths and potentially cause limited information disclosure or kernel DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a network-reachable UAF-read candidate in the IPv6 receive path. Even though the observed sink is constrained to slow-path debug logging and no write primitive is shown, the lifetime class and packet-processing exposure justify manual review rather than auto-closure.

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

Patch: ipv6: fix possible UAF in icmpv6_rcv() [ Upstream
Commit: 7bff2c8fe5c35ae58bf73104f53db3676e6e5d94
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7bff2c8fe5c35ae58bf73104f53db3676e6e5d94

Changed files:
  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=7bff2c8fe5c35ae58bf73104f53db3676e6e5d94

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

The original Linux kernel CVE announcement for CVE-2026-53006 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53006

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:L/I:N/A:L
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/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: 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: YES
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).