[CVE-2026-68157][MODERATE 7.0] libceph: guard missing CRUSH type name lookup

[CVE-2026-68157][MODERATE 7.0] libceph: guard missing CRUSH type name lookup

[AL-KERNEL]

CVE: CVE-2026-68157
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: libceph: guard missing CRUSH type name lookup
Commit: c46d82c47afc968d6ee8ef4470fa2dd35b765c21
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c46d82c47afc968d6ee8ef4470fa2dd35b765c21
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68157
Analysis date: Mon, 10 Aug 2026 09:19:18 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A malformed Ceph CRUSH map with a parent bucket missing type name metadata can cause a NULL pointer dereference in libceph localized read selection, allowing a malicious or compromised Ceph monitor to crash connected kernel clients.

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

The original Linux kernel CVE announcement for CVE-2026-68157 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68157

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-2026-68157	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;*CWE-20;CWE-754;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A NULL pointer dereference in libceph localized read selection can occur when get_immediate_parent() processes a malformed CRUSH map where a parent bucket name exists but the matching bucket type name is missing. The kernel client can then dereference a NULL type_cn pointer while building locality metadata, leading to a kernel crash and denial of service. For the CVSS the PR:N is used because the attacker does not need privileges on the vulnerable client, but practical triggering usually requires a malicious or compromised Ceph monitor or control of cluster metadata. The issue is network reachable in Ceph deployments where the client accepts monitor supplied CRUSH maps. Impact is denial of service only, with no supported evidence of information disclosure or privilege escalation from this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE DANGER NULLPTR SIMPLEFIX NETWORK KERNEL_PANIC_PLUS_UAF LINUS KPANIC  KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* +2 Remote reachable / network-triggerable: malformed CRUSH map metadata is supplied to the kernel Ceph client through Ceph monitor controlled cluster state.
* +1 Reliable kernel crash / strong DoS: NULL type_cn dereference can crash the kernel during localized read parent lookup.
* +1 Availability impact realistic: impact is a host kernel crash, not only a warning or recoverable error.
* +1 Important filesystem/storage path: libceph CRUSH map and OSD locality logic affect distributed storage client behavior.
* -1 Rare/configuration-dependent exposure: requires Ceph client usage with localized reads and acceptance of malformed or malicious cluster metadata, typically from a malicious or compromised monitor.

Paranoid adjustment:

* Remove the -1 exposure reduction in environments where Ceph is deployed and monitor supplied CRUSH maps are a normal trusted network input. This raises the practical triage score to 5.

Not applied:

* No generic memory corruption bonus: the primitive shown is NULL pointer dereference, not UAF, double free, OOB write, type confusion, or arbitrary write.
* No privilege escalation bonus: no reclaim, overwrite, callback, stale object reuse, or refcount takeover is visible.
* No confidentiality or integrity impact: no information leak or write primitive is supported by the patch context.

## 3. Reachability analysis

A remote actor cannot usually trigger this against arbitrary hosts on the Internet, but the bug is network-influenced in Ceph deployments because the kernel client consumes CRUSH map metadata from Ceph monitors. Practical triggering likely requires a malicious or compromised Ceph monitor, control over cluster metadata, or a client connected to an attacker-controlled Ceph cluster. No local privileges on the vulnerable client are required once the client accepts the malformed CRUSH map. Namespaces do not materially lower or raise the requirement, because the key condition is Ceph client connectivity and trusted monitor metadata rather than a local userspace syscall surface. Call-site confidence: medium, because the changed function and described localized read lookup path are present, but full caller context is not included.

## 4. Severity interpretation

This behaves like an actionable Moderate issue rather than an Important-class vulnerability. The demonstrated impact is a remote or network-influenced kernel DoS through malformed storage metadata. Theoretical escalation is not supported by the patch, because the failure mode is a NULL pointer dereference and invalid pointer use in strcmp(), not a controllable memory corruption primitive. It should not be auto-closed in Ceph-exposed environments because a compromised monitor or malicious cluster can plausibly crash clients.

## 5. One-sentence report phrase

A malformed Ceph CRUSH map with a parent bucket missing type name metadata can cause a NULL pointer dereference in libceph localized read selection, allowing a malicious or compromised Ceph monitor to crash connected kernel clients.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: network-influenced kernel crash through Ceph monitor supplied metadata, paranoid ActionableScore reaches 5, and exposure depends strongly on deployment trust boundaries around Ceph monitors.

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

Patch: libceph: guard missing CRUSH type name lookup
Commit: c46d82c47afc968d6ee8ef4470fa2dd35b765c21
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c46d82c47afc968d6ee8ef4470fa2dd35b765c21

Commit description:

Localized read selection can walk a parent bucket whose name exists in
the CRUSH map while its type has no matching entry in type_names.
get_immediate_parent() then dereferences a NULL type_cn and passes an
invalid pointer into strcmp(), causing a null-ptr-deref.

Skip such malformed parent buckets unless both the bucket name and type
name metadata are present. This keeps malformed hierarchy data from
crashing locality lookup and safely falls back to "not local".

[ idryomov: add WARN_ON_ONCE ]

Cc: stable@vger.kernel.org
Fixes: 117d96a ("libceph: support for balanced and localized reads")
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Zhengchuan Liang <zcliangcn@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Assisted-by: Codex:GPT-5.4
Signed-off-by: Zhao Zhang <zzhan461@ucr.edu>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.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=c46d82c47afc968d6ee8ef4470fa2dd35b765c21

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

The original Linux kernel CVE announcement for CVE-2026-68157 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68157

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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 7.5

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).