[CVE-2026-80805][MODERATE 7.0] xfs: validate attr entry pointer before field access

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

CVE: CVE-2026-80805
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: xfs: validate attr entry pointer before field access
Commit: 0f82586741e39926542f621bafa424e237a04fa4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f82586741e39926542f621bafa424e237a04fa4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80805
Analysis date: Fri, 04 Sep 2026 12:16:51 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: NO

Summary:
An XFS attribute leaf verifier can read local or remote attribute entry fields before validating that the entry pointer is inside the metadata buffer, allowing crafted filesystem metadata to trigger an out-of-bounds read and potential local DoS during filesystem processing.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80805 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80805

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: NO

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-2026-80805	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80805 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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:N/A:H';CWE-125;*CWE-20;CWE-1284;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.1';DESCR 'xfs_attr3_leaf_verify_entry can access attr entry fields before checking that the computed local or remote entry pointer is inside the attr leaf buffer. A crafted XFS metadata block with nameidx pointing near the end of the buffer can therefore cause an out-of-bounds read before the later name_end bounds validation runs. For the CVSS the PR:L is used in the paranoid score because a non-root local actor may be able to supply a crafted filesystem image to a delegated mount workflow, container environment, test runner, or other privileged helper, even though direct mounting usually requires administrator privileges. The issue is not network reachable and normally requires local processing of a crafted or corrupted XFS filesystem. Impact is at least denial of service via kernel crash or filesystem processing failure. A limited confidentiality impact is kept only for the paranoid score because the primitive is an out-of-bounds read, but there is no clear direct information disclosure path in the shown code.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 4)	YES	WRITE OOB DISK SIMPLEFIX IMPROVEONLY LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Paranoid score signals:

* Local unprivileged trigger: +1
  A non-root local actor may be able to provide a crafted XFS image or corrupted metadata to a delegated mount workflow, container setup, test runner, storage automation, or privileged helper.

* Memory corruption, weak or indirect corruption candidate: +1
  The primitive is an out-of-bounds read from an attacker-influenced on-disk metadata structure before the entry pointer is validated. This is not an OOB write, UAF, or arbitrary write.

* Reliable kernel crash / strong DoS: +1
  Crafted metadata can cause invalid kernel reads during XFS attribute leaf verification and can plausibly lead to kernel crash, mount failure, filesystem processing failure, or forced filesystem shutdown.

* Important filesystem/storage path: +1
  XFS metadata parsing and verification is an important filesystem integrity path.

* Confidentiality impact plausible: +1
  The primitive is read-only OOB. There is no demonstrated disclosure channel, so this is only a limited paranoid confidentiality concern, not strong information disclosure.

Conservative score rationale:

* Direct mounting or attaching arbitrary XFS filesystems normally requires root or CAP_SYS_ADMIN, so the conservative path applies a privilege penalty.
* No integrity impact is awarded because the patch shows bounds checking before field reads only. It does not show OOB write, stale pointer reuse, page-cache corruption, CoW bypass, or metadata overwrite.

## 3. Reachability analysis

The bug is triggered by processing crafted or corrupted XFS attribute leaf metadata. Direct exploitation normally requires local administrative ability to mount or otherwise make the kernel parse the crafted filesystem. Namespaces and containers can change the practical risk if a workflow allows less trusted users to submit filesystem images to a privileged mounter or storage service. The path is not network reachable by itself. XFS is broadly deployed, but the crafted metadata input requirement makes this less exposed than a syscall-only local bug.

Call-site confidence: medium. The patch clearly shows the verifier reading lentry/rentry fields before bounds validation, but the provided input does not include all callers and all mount/scrub/runtime verification paths.

## 4. Severity interpretation

This is best treated as an Actionable Moderate issue for triage, not an ordinary auto-close Low. The realistic impact is mainly local DoS or filesystem processing failure. Theoretical confidentiality impact exists only because this is an OOB read in kernel metadata parsing, but there is no clear user-visible leak primitive. Privilege escalation is not supported by the patch.

## 5. One-sentence report phrase

An XFS attribute leaf verifier can read local or remote attribute entry fields before validating that the entry pointer is inside the metadata buffer, allowing crafted filesystem metadata to trigger an out-of-bounds read and potential local DoS during filesystem processing.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

YES REQUIRES MANUAL CHECK. This is a filesystem metadata parser issue with an OOB read primitive in an important storage path, but no OOB write, UAF, page-cache corruption, or clear privilege escalation primitive is shown.

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

Patch: xfs: validate attr entry pointer before field access
Commit: 0f82586741e39926542f621bafa424e237a04fa4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f82586741e39926542f621bafa424e237a04fa4

Commit description:

xfs_attr3_leaf_verify_entry() accesses lentry/rentry fields (namelen,
valuelen) before checking if the entry pointer itself is within bounds.
If nameidx is crafted to point near the end of the buffer, these field
accesses can read out-of-bounds before the bounds check at
name_end > buf_end is performed.

Add explicit bounds checks for entry pointers before accessing their
fields. Use offsetof() to check that the start of the flexible array
member (nameval/name) is within bounds, which ensures all preceding
fields are safe to access.

Fixes: c847606 ("xfs: check attribute leaf block structure")
Cc: <stable@vger.kernel.org> # v5.5
Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  fs/xfs/libxfs/xfs_attr_leaf.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=0f82586741e39926542f621bafa424e237a04fa4

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

The original Linux kernel CVE announcement for CVE-2026-80805 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80805

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:H/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:N/A:H
  The Best / paranoid CVSS score: 6.1

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: 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: NO
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).