[CVE-2026-80558][MODERATE 7.0] libceph: Avoid using invalid osd indices from primary_temp

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

CVE: CVE-2026-80558
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: libceph: Avoid using invalid osd indices from primary_temp
Commit: 505fc50b8ff8e687b7e3ef6866269dea27366224
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=505fc50b8ff8e687b7e3ef6866269dea27366224
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80558
Analysis date: Wed, 26 Aug 2026 13:37:39 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80558 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80558

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80558	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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:L/A:H';CWE-125;CWE-129;*CWE-20;BEST CVSS score: '7';DESCR 'A corrupted Ceph osdmap received from a monitor or OSD can contain an invalid primary_temp OSD index that is outside the valid 0 to max_osd range. libceph could accept this value as the target OSD for a request and then use it to read osd_state, osd_weight, or osd_addr arrays out of bounds. For the CVSS the PR:N is used because the attacker does not need local privileges on the victim host, but practical triggering usually requires a malicious or compromised Ceph monitor or OSD, or the ability to tamper with trusted Ceph cluster traffic. The issue is network reachable in Ceph deployments where the client accepts osdmaps from a reachable cluster endpoint, but these networks are normally internal storage networks rather than public Internet services. Impact is at least denial of service and may include limited confidentiality or integrity impact because an out of bounds read can influence target selection or consume unintended kernel memory values.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 7)	YES	REMOTE OOB DANGER SIMPLEFIX NETWORK LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=5

1. ActionableScore
* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Remote reachable / network-triggerable: +2. The malformed `osdmap` is received from a Ceph monitor or OSD over the cluster network. Practical triggering likely requires a malicious or compromised Ceph endpoint or traffic tampering.
* Memory corruption, weak/indirect corruption candidate: +1. The bug is an unchecked OSD index from `primary_temp`, causing out-of-bounds reads from `osd_state`, `osd_weight`, and `osd_addr` arrays.
* Reliable kernel crash / strong DoS: +1. Invalid array indexing in kernel Ceph client request targeting can plausibly crash or destabilize the client.
* Confidentiality impact plausible: +1. The OOB read may consume unintended kernel memory values, though no direct user-visible leak primitive is shown.
* Integrity impact plausible, paranoid only: +1. In the worst defensible case, a wrong target OSD decision could influence request routing or state decisions, but there is no OOB write or arbitrary write primitive.
* Important filesystem/storage path: +1. Ceph is a kernel storage client path and request targeting affects distributed storage access.
* Rare/internal deployment exposure: -1. Ceph cluster networks are usually internal storage networks, not public Internet services.
* Call-site confidence: high. The commit describes the downstream call path through `ceph_pg_to_up_acting_osds()` and `calc_target()` and identifies the affected arrays.

3. Reachability analysis
A remote Ceph monitor or OSD can supply the corrupted `osdmap`, but a random Internet attacker normally cannot unless the Ceph cluster network is exposed or the attacker controls or compromises a cluster endpoint. No local privileges are required on the victim host in the network-threat model. Containers and namespaces do not materially change reachability unless they can influence the Ceph client configuration or cluster endpoint selection. The path is not default for all Linux systems, but it is relevant on systems using kernel Ceph clients.

4. Severity interpretation
This is more than an ordinary Moderate because it is network-influenced OOB read in a kernel storage client. It does not look like a strong Important memory-corruption case because the primitive is read-only array over-indexing, with no demonstrated overwrite, UAF reclaim, type confusion, callback control, or arbitrary write. Conservative handling is Actionable Moderate. Paranoid handling reaches the upper Moderate range because limited confidentiality or integrity side effects are technically plausible from consuming unintended kernel array-adjacent values.

5. One-sentence report phrase
A corrupted Ceph osdmap from a monitor or OSD can provide an invalid primary_temp index, causing libceph to select a nonexistent target OSD and perform out-of-bounds reads in OSD state, weight, or address arrays, with likely DoS and limited worst-case confidentiality or integrity concern.

6. Manual review recommendation
MANUAL CHECK REQUIRED. This is network-influenced kernel OOB read in a storage path, and although no write primitive is shown, the combination of remote cluster input, request target selection, and kernel array access should not be auto-closed.

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

Patch: libceph: Avoid using invalid osd indices from primary_temp
Commit: 505fc50b8ff8e687b7e3ef6866269dea27366224
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=505fc50b8ff8e687b7e3ef6866269dea27366224

Commit description:

A corrupted osdmap received from a Ceph monitor or OSD may contain osd
indices in its pg_temp, primary_temp, pg_upmap, and pg_upmap_items parts
that don't exist, i.e., that are greater than max_osd or smaller than
CEPH_HOMELESS_OSD (-1). These indices are used to create the up and
acting set in ceph_pg_to_up_acting_osds(), called from calc_target().
While most of these osd indices are checked, the one from primary_temp
is not. Subsequently, this may lead to calc_target() returning this
(potentially invalid) index as target osd for a (linger) request.
Because the osd_state, osd_weight, and osd_addr arrays only contain
max_osd entries (with indices 0 to max_osd -1), this leads to
out-of-bounds accesses when trying to read values from these arrays.

This patch fixes the issue by adding a check to get_temp_osds(), so that
only valid osd indices from primary_temp are used, and it falls back to
using the primary from pg_temp or the up set if it is invalid.

[ idryomov: changelog ]

Cc: stable@vger.kernel.org
Fixes: 5e8d4d3 ("libceph: add support for primary_temp mappings")
Signed-off-by: Raphael Zimmer <raphael.zimmer@tu-ilmenau.de>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/ceph/osdmap.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=505fc50b8ff8e687b7e3ef6866269dea27366224

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

The original Linux kernel CVE announcement for CVE-2026-80558 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80558

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: Not available
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/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: 5
  Paranoid ActionableScore: 6

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).