[CVE-2026-89608][MODERATE REGULAR] ecryptfs: pass packet set buffer size to parser

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

CVE: CVE-2026-89608
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ecryptfs: pass packet set buffer size to parser
Commit: 329de8b9e988b152b938f09224670d97bada0b96
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=329de8b9e988b152b938f09224670d97bada0b96
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89608
Analysis date: Sat, 12 Sep 2026 03:14:26 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-89608 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89608

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 REGULAR
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-2026-89608	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-89608 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-125;CWE-130;*CWE-20;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.6';DESCR 'An eCryptfs packet parser can overstate the remaining header buffer because ecryptfs_parse_packet_set used a PAGE_SIZE based limit instead of the actual packet set length passed by the caller. For version 1 headers the packet set may start later in the page, so malformed on disk metadata can make tag 3 or tag 11 parsing operate with a limit that extends past the real packet buffer. For the CVSS the PR:L is used because a local user or local process must be able to supply or access a crafted eCryptfs file header in an affected mount or lower filesystem path. The issue is not directly network reachable and is triggered through local filesystem metadata parsing rather than packet traffic. Impact is at least local denial of service via parser failure or possible kernel crash. In the paranoid interpretation it may allow limited confidentiality or integrity impact due to an out of bounds read primitive, but the patch does not support treating it as an out of bounds write or confirmed privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)  SKIP CVE-2026-89608 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	OOB DISK SIMPLEFIX LINUS MEMORY PACKET  DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 4
* Paranoid score: 4
* No floor or cap changed the score.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Conservative positive signals:

* +1 Local below-host-admin filesystem trigger. A local user or local process that can place or access crafted eCryptfs file metadata in an affected eCryptfs mount can reach the parser path.
* +1 Weak corruption or invalid-read candidate. The parser used a PAGE_SIZE based remaining length after receiving a pointer already offset into the header page, which can overstate the valid packet buffer and allow parsing beyond the intended packet-set region.
* +1 Filesystem metadata parser path. The bug is in eCryptfs encrypted header packet parsing, which is security-relevant filesystem metadata handling.

Paranoid additional signal:

* +1 Possible kernel crash / DoS. If malformed packet sizes drive parsing beyond the real buffer limit, the most defensible stronger consequence is parser failure or possible kernel fault, not privilege escalation.

Non-awarded material signals:

* RealUAF not awarded. The patch does not establish stale object use, refcount misuse, double release, or post-lifetime access.
* CLASS_A not awarded. No controlled overwrite, controlled reclaim, arbitrary write, COW ownership violation, or authorization bypass is shown.
* Confidentiality not awarded as an ActionableScore signal. The bug is an internal OOB read candidate, but no concrete read-back or disclosure path to userspace, network, or another principal is established.
* Integrity not awarded. No OOB write, metadata overwrite, unauthorized modification, or ownership/COW bypass is established.
* Remote reachability not awarded. The trigger is local filesystem metadata parsing, not network packet processing.
* Reliable crash is only used in the paranoid score. The patch supports a bounds overread risk, but does not provide a demonstrated panic trace.
* ImportantCandidate not set. The established primitive is bounded parser overread / invalid-state behavior without demonstrated memory corruption useful beyond DoS.

3. Reachability analysis

The likely attacker is a local user or local process able to cause eCryptfs to parse a crafted encrypted file header. This may occur through an existing eCryptfs mount or a lower filesystem path containing malformed eCryptfs metadata. The supplied evidence supports below-host-admin reachability for the parsing operation, so HostAdminRequired=NO.

Namespace-scoped privilege is not relevant from the supplied patch. There is no evidence that the complete trigger depends on a user namespace or network namespace, so NamespaceScopedPrivilege=NO.

There is likely prior system setup in the sense that eCryptfs must be enabled and an affected eCryptfs mount or file header path must exist. That does not by itself make the attacker host admin. No special hardware, firmware, network service, or race timing is required. The issue is data-driven parser behavior rather than a timing race.

4. Primitive and severity interpretation

The exact primitive is an eCryptfs packet parser bounds error. ecryptfs_parse_packet_set() previously received a pointer into the file header but calculated remaining space as PAGE_SIZE - 8. For version 1 headers the packet set can start later than that, so the remaining length can be overstated. The parser can then pass excessive limits to tag 3 and tag 11 parsing.

This is not an active structured-object UAF and not fixed stale storage. It is a local filesystem metadata parser invalid-read / bounds-checking flaw. There is no concrete repeated release/refcount operation. There is no first lifetime operation that may free an object and no second lifetime mutation through a dangling reference.

PrimitiveClass=CLASS_C because the demonstrated behavior is invalid parser bounds handling with possible crash/DoS, without an independently useful corruption primitive. The practical demonstrated consequence is local DoS or parser failure. A limited OOB read is plausible, but disclosure is not established. Privilege escalation is speculative and not supported by the patch.

ImportantCandidate=NO because the patch does not establish UAF, write corruption, controlled reclaim, authorization bypass, or a filesystem ownership/COW violation. AutoDowngradeAllowed=YES because no unresolved Class A or strong Class B primitive remains. Manual review is still recommended because filesystem parser bounds bugs can be underestimated and the parser helper internals may affect whether the overread becomes only EIO, a fault, or a limited disclosure path.

Likely operational severity is Borderline / Actionable Moderate only if the environment has untrusted users able to feed malformed eCryptfs metadata. Otherwise it is closer to ordinary Moderate.

5. One-sentence report phrase

An eCryptfs packet parser length calculation can overstate the remaining header buffer for version 1 headers, allowing malformed local filesystem metadata to drive tag parsing beyond the real packet-set buffer and potentially cause parser failure or kernel DoS.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

The issue is a filesystem parser bounds bug with a plausible OOB read candidate, but the supplied patch does not establish UAF, OOB write, disclosure, privilege escalation, or an authorization boundary bypass.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ecryptfs: pass packet set buffer size to parser
Commit: 329de8b9e988b152b938f09224670d97bada0b96
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=329de8b9e988b152b938f09224670d97bada0b96

Commit description:

ecryptfs_parse_packet_set() receives a pointer into the file header, but
it calculates the remaining packet buffer size from PAGE_SIZE - 8.  For
version 1 headers the packet set starts later in the header, so this can
overstate the available buffer.

Pass the actual packet set buffer length from the caller and calculate
per-packet limits from the remaining bytes in that buffer.  Recompute the
remaining length after consuming a tag 3 packet before parsing the
following tag 11 packet.

Fixes: 237fead ("[PATCH] ecryptfs: fs/Makefile and fs/Kconfig")
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/crypto.c
  fs/ecryptfs/ecryptfs_kernel.h
  fs/ecryptfs/keystore.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=329de8b9e988b152b938f09224670d97bada0b96

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

The original Linux kernel CVE announcement for CVE-2026-89608 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89608

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:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.6

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: 3
  Paranoid ActionableScore: 4

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).