[CVE-2026-89609][MODERATE 7.0] ecryptfs: hold msg ctx list lock when cleaning daemon queue

[CVE-2026-89609][MODERATE 7.0] ecryptfs: hold msg ctx list lock when cleaning daemon queue

[AL-KERNEL]

CVE: CVE-2026-89609
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ecryptfs: hold msg ctx list lock when cleaning daemon queue
Commit: 7e48afafe7abc275f7b6916613bb18b821e7d94a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7e48afafe7abc275f7b6916613bb18b821e7d94a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89609
Analysis date: Fri, 11 Sep 2026 20:17:18 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-89609 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89609

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-2026-89609	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-89609 CHECK WITH IMPACT FROM ORIG NN LOW	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-362;CWE-667;*CWE-416;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'eCryptfs daemon cleanup can move queued message contexts back to the global free list without holding the global message context list mutex. This can race with other kernel users of the same message context lists and may corrupt list state during daemon teardown. For the CVSS the PR:L is used because a local user or local eCryptfs helper context is normally needed to exercise the daemon cleanup path. The issue is not network reachable and requires local interaction with eCryptfs state. Impact is at least local denial of service via kernel crash. In the paranoid interpretation the race is a kernel list handling memory corruption candidate and may allow confidentiality or integrity impact if corrupted list pointers are later reused.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate (with actual score 5)  SKIP CVE-2026-89609 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	LOCK DISK SIMPLEFIX HARDWARE LINUS  KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate**::

No floor or cap changed the score.

2. Signal breakdown

Conservative positive signals:

* +2: Concrete CLASS_B kernel list or object state corruption candidate. `ecryptfs_exorcise_daemon()` moves queued `msg_ctx` objects back to the global free list without holding `ecryptfs_msg_ctx_lists_mux`, while `ecryptfs_msg_ctx_alloc_to_free()` requires that lock.
* +1: Realistic kernel DoS risk. Unsynchronized `list_del()` plus global free-list mutation can corrupt list state or expose inconsistent message context state to other users, plausibly leading to WARN, BUG, Oops, or crash.
* +1: Security-relevant filesystem messaging path. The affected code is in eCryptfs daemon messaging and message context lifetime management, not passive diagnostic state.

Paranoid additional signal:

* +1: Weak unresolved exploitation concern. The affected objects are active message context structures returned to a shared global free list, so a race could plausibly cause reuse or inconsistent ownership of a context beyond a simple immediate NULL dereference. This does not prove controlled reclaim or LPE.

Negative signals:

* 0: No host-admin penalty. Host-admin-equivalent privilege is not positively established from the supplied patch.
* 0: No race penalty. The bug is a race, but the evidence does not prove a narrow, one-shot, externally uncontrollable timing window.
* 0: No niche-subsystem penalty. eCryptfs may be less commonly used, but rarity plus inability for an attacker to reach it is not established.

Important non-awarded signals:

* Controlled reclaim is not demonstrated.
* Arbitrary write is not demonstrated.
* RealUAF is not set because the patch does not directly establish a post-free stale object dereference.
* Concrete repeated release or refcount mutation is not established.
* Structured stale-object leverage is not separately awarded as a strong primitive.
* Weak LPE is not awarded beyond the paranoid weak unresolved concern.
* Extra Availability is not awarded because the plausible crash and availability impact are the same consequence.
* C/I-style impact is not awarded merely because list corruption could theoretically affect reclaimed memory.
* Remote reachability is not established.

Concrete repeated-release/refcount check:

* First release can end lifetime: not established.
* Exact same reference survives after a lifetime-ending release: not established.
* Second operation is a concrete lifetime/refcount mutation: not established.
* +1 Concrete repeated release/refcount: not awarded.
* Paranoid repeated-refcount leverage +1: not awarded.
* FLOOR 5 for repeated release/refcount: not applied.

3. Reachability analysis

The vulnerable path is local eCryptfs daemon cleanup in `ecryptfs_exorcise_daemon()`. A trigger likely requires local interaction with eCryptfs state and a dying daemon that has queued outbound message contexts.

Ordinary unprivileged reachability is not fully established by the supplied context. eCryptfs can be used in user-session style deployments, but the complete privilege boundary for mounting, daemon setup, and cleanup is not shown in the patch. Therefore `HostAdminRequired=UNKNOWN`, not YES and not NO.

No network trigger is indicated. The issue is not packet-driven and has no direct remote attack surface from the supplied patch.

No namespace-scoped capability chain is established. `NamespaceScopedPrivilege=NO`.

Prior setup may exist in practice if an eCryptfs mount and userspace daemon must already be active, but the supplied evidence does not prove that such setup requires host-admin-equivalent privilege for all deployments.

No special hardware, firmware, boot mode, or rare physical device prerequisite is indicated.

The race is between daemon queue cleanup and other global message context list users. The supplied evidence does not prove the timing is narrow enough to apply a hard-race penalty.

4. Primitive and severity interpretation

The exact primitive is missing synchronization around active kernel list and message context state. `ecryptfs_exorcise_daemon()` removes contexts from a daemon queue and returns them to the global free list without the global list mutex required by the helper.

This is an active structured object/list consistency bug, not fixed stale storage. The operation occurs during cleanup of a dying daemon, but the stale or inconsistent state can affect a global pool used by other message context users.

A concrete repeated release/refcount operation is not established. The patch does not show a first lifetime-ending put followed by a second put on the same dangling reference.

Primitive classification is `CLASS_B` because the patch establishes a real kernel synchronization and list-state corruption candidate with unresolved exploitation consequences. It is not `CLASS_A` because there is no controlled reclaim, directed write, callback control, demonstrated LPE, or authorization bypass. It is not `CLASS_C` because the issue is not merely a passive warning or simple invalid dereference.

The demonstrated consequence is mainly local denial of service through list corruption or crash. The speculative consequence is broader memory corruption if corrupted list state or prematurely reused message contexts are consumed by other eCryptfs messaging paths. That possibility is technically plausible but not strong enough to classify as Important.

`ImportantCandidate=NO` because the patch does not establish controlled exploitation leverage beyond corruption risk and DoS. `AutoDowngradeAllowed=NO` because automatically closing this as ordinary low/moderate would lose an unresolved concrete kernel list corruption primitive in a security-relevant filesystem messaging path.

Likely operational severity is actionable Moderate, with manual review recommended.

5. One-sentence report phrase

eCryptfs daemon cleanup can race with other global message context list users because queued contexts are returned to the global free list without holding the required mutex, which can corrupt list state and lead to local denial of service with unresolved memory corruption risk.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because this is not just a cosmetic locking fix. The missing lock protects global message context list state, and the corruption consequences depend on concurrent users of the same context pool.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ecryptfs: hold msg ctx list lock when cleaning daemon queue
Commit: 7e48afafe7abc275f7b6916613bb18b821e7d94a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7e48afafe7abc275f7b6916613bb18b821e7d94a

Commit description:

ecryptfs_exorcise_daemon() drops queued messages from a dying daemon
without holding ecryptfs_msg_ctx_lists_mux, but
ecryptfs_msg_ctx_alloc_to_free() requires that lock.

Take the list lock while moving the queued contexts back to the free
list to avoid racing with other global msg ctx list users.

Fixes: f66e883 ("eCryptfs: integrate eCryptfs device handle into the module.")
Cc: <stable@vger.kernel.org>
Signed-off-by: Yichong Chen <chenyichong@uniontech.com>
Signed-off-by: Tyler Hicks <code@tyhicks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  fs/ecryptfs/messaging.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=7e48afafe7abc275f7b6916613bb18b821e7d94a

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

The original Linux kernel CVE announcement for CVE-2026-89609 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89609

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:N/I:N/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: 4
  Paranoid ActionableScore: 5

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).