[CVE-2026-68335][IMPORTANT] rds: drop incoming messages that cross network namespace boundaries [ Upstream

[CVE-2026-68335][IMPORTANT] rds: drop incoming messages that cross network namespace boundaries [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68335
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: rds: drop incoming messages that cross network namespace boundaries [ Upstream
Commit: 1e2e2d9806944fe485824d617c8b7c78116c22db
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1e2e2d9806944fe485824d617c8b7c78116c22db
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68335
Analysis date: Mon, 10 Aug 2026 18:34:58 -0400
ActionableScore: 8
ActionableScore lower bound: 7
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
RDS can deliver messages across network namespace boundaries, leaving an incoming message with a stale rds_connection pointer after netns teardown and causing a UAF that can crash the kernel and may plausibly support privilege escalation through a freed transport callback.

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

The original Linux kernel CVE announcement for CVE-2026-68335 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68335

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-2026-68335	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-668;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'RDS can deliver an incoming message across network namespace boundaries because rds_find_bound uses a global lookup key that does not include the network namespace. This can leave inc i_conn pointing to an rds_connection from netns A while the receiving socket lives in netns B. After netns A is destroyed, cleanup_net can free that connection while the survivor socket still holds the incoming message, so later receive queue cleanup can dereference freed memory or call through a freed transport pointer. For the CVSS the PR:L is used because triggering requires local code execution, but the described path is reachable from unprivileged user namespaces with CLONE_NEWUSER and CLONE_NEWNET. The issue is not directly network reachable in the usual CVSS sense. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to a use-after-free with a possible function pointer call through a freed object.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)  SKIP CVE-2026-68335 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	INIT RACE UAF  KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6	-	-	checked

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

ActionableScore=8
ActionableScoreLower=7

## 1. ActionableScore

* Conservative score: 7
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. The description states reachability from unprivileged user namespaces using CLONE_NEWUSER and CLONE_NEWNET.
* Generic memory corruption: +2. The bug is a real use-after-free on inc->i_conn after rds_connection is freed during netns cleanup.
* Real lifetime corruption: +1. The stale rds_connection pointer survives netns teardown and is later dereferenced from a surviving socket.
* Reliable kernel crash / strong DoS: +1. KASAN confirms a UAF read through inc->i_conn->c_lcong.
* Weak LPE concern: +1. The second dangerous site may call inc->i_conn->c_trans->inc_free(inc) through a freed object, but no controlled reclaim or replacement is demonstrated.
* Cross-boundary isolation/policy bypass: +1. The root cause is cross-network-namespace message delivery caused by a global netns-agnostic socket lookup.

Paranoid upgrade:

* Privilege escalation plausible: +2 instead of weak +1. The potential call-through-freed-object primitive gives a defensible higher-risk interpretation, even though exploitation reliability is not proven.

Not counted:

* Remote reachable: +0. This is not directly network-triggerable in normal CVSS sense.
* Hard race penalty: 0. The sequence depends on netns lifetime and message retention, but the described path is more than a purely accidental timing-only race.
* Rare subsystem penalty: 0. RDS is not universally deployed, but the path is reachable through ordinary local namespace/socket behavior when available.

## 3. Reachability analysis

A local unprivileged user can plausibly trigger the bug if unprivileged user namespaces and network namespaces are enabled and RDS is available. The attack uses netns separation to create a connection in one namespace and a receiving socket in another, then relies on cleanup_net freeing the connection while the survivor socket still holds the incoming message. Containers and delegated namespaces matter because they can reduce the effective privilege requirement from host-admin to local unprivileged or container-level code execution. The issue is not directly Internet-reachable, but it crosses a namespace boundary and affects kernel networking lifetime semantics.

## 4. Severity interpretation

This behaves like an Important-class candidate rather than an ordinary Moderate. The demonstrated impact includes a confirmed UAF read and a plausible callback-through-freed-object path, which is stronger than a simple NULL dereference or resource leak. Realistic exploitation evidence for full privilege escalation is not demonstrated, so the conservative score stays below high-end Important. The paranoid score is justified because UAF plus possible function pointer use after free is exactly the class that often requires manual kernel security review.

## 5. One-sentence report phrase

RDS can deliver messages across network namespace boundaries, leaving an incoming message with a stale rds_connection pointer after netns teardown and causing a UAF that can crash the kernel and may plausibly support privilege escalation through a freed transport callback.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: confirmed UAF, namespace-boundary crossing, local unprivileged reachability, and a possible call-through-freed-object primitive make this unsuitable for auto-close.

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

Patch: rds: drop incoming messages that cross network namespace boundaries [ Upstream
Commit: 1e2e2d9806944fe485824d617c8b7c78116c22db
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1e2e2d9806944fe485824d617c8b7c78116c22db

Changed files:
  net/rds/recv.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=1e2e2d9806944fe485824d617c8b7c78116c22db

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

The original Linux kernel CVE announcement for CVE-2026-68335 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68335

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:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 7
  Paranoid ActionableScore: 8

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).