* [CVE-2026-89559][MODERATE 7.0] libnvdimm/labels: Prevent integer overflow in __nd_label_validate()
@ 2026-09-12 10:02 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-12 10:02 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89559
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: libnvdimm/labels: Prevent integer overflow in __nd_label_validate()
Commit: e057efcc9c71d90099d9ee00bed0748d0e9fd586
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e057efcc9c71d90099d9ee00bed0748d0e9fd586
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89559
Analysis date: Sat, 12 Sep 2026 06:02:13 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89559 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89559
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-2026-89559 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89559 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:H/I:H/A:H';CWE-190;*CWE-787;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H';BEST CVSS score: '7.8';DESCR 'An integer overflow in libnvdimm label validation can allow a crafted namespace index nslot value to pass the config area bounds check. The overflow happens before comparing nslot multiplied by the runtime namespace label size against the NVDIMM config size, so a very large on media or userspace supplied value can wrap to a small value and be accepted. The accepted nslot is later used as a loop count in label data initialization, where memset can write past the end of the config buffer. For the CVSS the PR:L is used for the paranoid score because a local process with delegated access to the nvdimm config interface or device permissions may be able to provide crafted label data without full host administrator control. The issue is not network reachable. Impact is kernel memory corruption with at least denial of service and a plausible path to confidentiality and integrity impact, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6) YES WRITE OOB SIMPLEFIX IMPROVEONLY KPANIC MEMORY DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 5
* Conservative score: 5. No floor or cap changed the score.
* Raw paranoid score: 6
* Paranoid score: 6. No floor or cap changed the score.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Conservative signals:
* +2. Concrete attacker-influenced kernel out-of-bounds write. A crafted u32 nslot can make the 32-bit multiplication wrap, pass validation, and later drive memset beyond the config_size buffer.
* +1. Reliable kernel crash or strong DoS is plausible because the bug writes past a kernel buffer during label data initialization.
* +1. Memory layout invariant restoration. The patch restores the intended invariant between nslot, runtime label size, namespace index overhead, and the actual config area size.
* +1. Important storage namespace metadata path. The bug affects libnvdimm namespace label validation and can be reached from untrusted on-media label data or userspace-provided config data.
Paranoid additional signal:
* +1. Integrity impact is plausible because the primitive is a real kernel out-of-bounds write, even though payload and target control are constrained.
Important non-awarded signals:
* Controlled reclaim is not demonstrated.
* Arbitrary write is not demonstrated.
* Confidentiality impact is not awarded because no read-back or disclosure path is shown.
* Remote reachability is not established.
* RealUAF is not present.
* Concrete repeated release or refcount mutation is not present.
* Extra Availability is not awarded because the same crash/DoS is already counted once.
* Stronger LPE points are not separately awarded because no credential overwrite, callback control, arbitrary R/W, or demonstrated privilege-escalation chain is supplied.
3. Reachability analysis
The attacker-controlled field is nslot, read from the NVDIMM on-media namespace index area or supplied from userspace through ND_CMD_SET_CONFIG_DATA. This establishes untrusted input, but the complete privilege boundary for the userspace command is not fully resolved from the supplied patch alone.
HostAdminRequired is UNKNOWN. Host-admin-equivalent access may be common for NVDIMM configuration, but the evidence does not positively prove that host admin is always required. Below-host-admin delegated device access is plausible but not proven as ordinary unprivileged reachability.
NamespaceScopedPrivilege is NO. This is not a namespace-scoped networking or container capability path.
The issue is not network reachable. A prior NVDIMM or persistent memory device, emulation, or userspace access to the NVDIMM config interface is needed. No race or timing condition is involved, so no race penalty applies.
4. Primitive and severity interpretation
The exact primitive is an integer-overflow-induced bounds-check bypass followed by a kernel out-of-bounds memset. The accepted crafted nslot becomes a loop trip count in nd_label_data_init, allowing writes past the end of the config_size buffer.
This is not an active-object UAF and not fixed stale storage. It is a direct kernel memory corruption primitive. The write payload appears constrained, likely memset-style zeroing, and the target is adjacent memory beyond the config buffer rather than an attacker-selected arbitrary address. That limits confidence in immediate LPE, but it does not make the issue crash-only.
PrimitiveClass is CLASS_A because a concrete attacker-influenced OOB write is established. ImportantCandidate is YES because kernel memory corruption with untrusted input and unresolved exploitation leverage should not be automatically downgraded. AutoDowngradeAllowed is NO because the primitive is concrete kernel corruption, not a warning, leak, or pure DoS-only logic bug.
Likely operational severity is actionable Moderate at minimum, with Strong Important candidate review warranted depending on actual device permissions, allocation layout, and whether the OOB zeroing can corrupt security-relevant adjacent kernel state.
5. One-sentence report phrase
An integer overflow in libnvdimm label validation allows a crafted nslot value from NVDIMM label media or ND_CMD_SET_CONFIG_DATA to bypass the config size check and drive an out-of-bounds memset past the namespace label buffer, creating kernel memory corruption and at least a local DoS risk with unresolved privilege escalation potential.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: the patch establishes a concrete kernel out-of-bounds write from untrusted label/config data, and the practical privilege boundary and exploitability of the adjacent-memory corruption need manual validation.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: libnvdimm/labels: Prevent integer overflow in __nd_label_validate()
Commit: e057efcc9c71d90099d9ee00bed0748d0e9fd586
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e057efcc9c71d90099d9ee00bed0748d0e9fd586
Commit description:
The on-media namespace index field nslot is a u32 read from the DIMM
label storage area. __nd_label_validate() bounds it against the config
area size, but sizeof_namespace_label() returns unsigned, so the product
nslot * label_size is evaluated in 32-bit and wraps modulo 2^32 before
the comparison. A crafted nslot passes the bound and is then used as the
loop trip count in nd_label_data_init(), whose memset() walks off the end
of the config_size buffer: an out-of-bounds write.
The field is not trusted -- it comes from the medium, or from userspace
via ND_CMD_SET_CONFIG_DATA. Evaluate the product in 64-bit so the bound
check is exact; conforming labels are unaffected.
The check was safe when introduced by commit 4a826c8 ("libnvdimm:
namespace indices: read and validate"): it multiplied by sizeof(struct
nd_namespace_label), a size_t, so on a 64-bit build the product did not
wrap. Commit 564e871 ("libnvdimm, label: add v1.2 nvdimm label
definitions") narrowed it to 32 bits when the label size became a runtime
value read via sizeof_namespace_label().
Fixes: 564e871 ("libnvdimm, label: add v1.2 nvdimm label definitions")
Cc: [email protected]
Reviewed-by: Alison Schofield <[email protected]>
Signed-off-by: Bryam Vargas <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Alison Schofield <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/nvdimm/label.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=e057efcc9c71d90099d9ee00bed0748d0e9fd586
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89559 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89559
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:H/I:H/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7.8
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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