* [CVE-2026-80963][LOW] dm-stats: fix a crash if allocation of per-cpu data fails
@ 2026-09-11 23:56 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-11 23:56 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-80963
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: dm-stats: fix a crash if allocation of per-cpu data fails
Commit: c3f211b7a277dd404b4e7d23095be964b5b46a27
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c3f211b7a277dd404b4e7d23095be964b5b46a27
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80963
Analysis date: Fri, 11 Sep 2026 19:56:28 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80963 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80963
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: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-80963 LOW https://www.kernelcve.org/list/?q=CVE-2026-80963 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-703;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A NULL pointer dereference can occur in dm-stats cleanup when allocation of per CPU statistics data fails and dm_stat_free later dereferences s stat_percpu for a CPU where the pointer was never initialized. The issue is in the error handling path for partial allocation failure, so reliable triggering normally requires local control of device mapper statistics plus memory pressure or allocation failure conditions. For the CVSS the PR:L is used in the paranoid score because delegated device mapper control or reduced admin contexts can make the trigger available to a less privileged local actor. The issue is not network reachable. Impact is denial of service via kernel crash only, with no evidence of UAF, out of bounds write, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES DANGER NULLPTR DISK SIMPLEFIX LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: -1
* Conservative score: 1
* Raw paranoid score: -1
* Paranoid score: 1
* Applied floor/cap: raw score clamped from -1 to 1 as a nonzero ordinary kernel DoS triage score.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Positive signals:
* +1 Reliable kernel crash / strong DoS: allocation failure in dm_kvzalloc can send control flow to dm_stat_free, which dereferences s->stat_percpu[cpu] while it is NULL and crashes.
* +0 Weak corruption concern: this is a NULL pointer dereference in cleanup, not an independently useful corruption primitive.
Negative signals:
* -2 Host-admin-equivalent privilege required: device-mapper statistics management is normally reached through privileged device-mapper control operations requiring host administrative privileges.
Material non-awarded signals:
* RealUAF not awarded: no stale post-lifetime object use is established.
* Concrete repeated release/refcount not awarded: the patch adds a NULL check before freeing per-cpu storage, but there is no first release followed by a second lifetime mutation on the same dangling reference.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Information disclosure not demonstrated.
* Privilege escalation not demonstrated.
* Remote reachability not established.
* Extra availability point not awarded because the same NULL dereference crash is already counted once.
* C/I impact not awarded because the evidence supports DoS only.
3. Reachability analysis
Triggering requires local ability to configure or create dm-stats state and to reach the allocation failure path during per-cpu statistics setup. In normal Linux deployments, device-mapper control is host-admin-equivalent and not namespace-scoped for an ordinary unprivileged user. The failure also depends on an allocation failure condition, but this is an ordered error path rather than a race. No network trigger, special hardware, or guest-to-host boundary is involved.
4. Primitive and severity interpretation
The primitive is an invalid NULL pointer dereference in dm_stat_free after partial initialization failure. The affected storage is not a freed active structured object and not a UAF. The stale-use and repeated-release exceptions do not apply. Demonstrated consequence is kernel crash / DoS. Speculative consequences beyond DoS are not supported by the patch. ImportantCandidate=NO because there is no memory corruption, ownership violation, authorization bypass, refcount mutation through a dangling object, or meaningful unresolved exploitation primitive. AutoDowngradeAllowed=YES because this is a constrained host-admin-triggered cleanup crash.
5. One-sentence report phrase
A dm-stats cleanup error can dereference a NULL per CPU statistics pointer after allocation failure, causing a local host-admin-triggered kernel crash without evidence of UAF, information disclosure, or privilege escalation.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
Reason: crash-only NULL dereference in a privileged device-mapper cleanup path, with no established corruption or security-boundary primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: dm-stats: fix a crash if allocation of per-cpu data fails
Commit: c3f211b7a277dd404b4e7d23095be964b5b46a27
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c3f211b7a277dd404b4e7d23095be964b5b46a27
Commit description:
If "dm_kvzalloc(percpu_alloc_size, cpu_to_node(cpu))" fails, the code
jumps to the "out" label and calls dm_stat_free. dm_stat_free does
"for_each_possible_cpu(cpu) { dm_kvfree(s->stat_percpu[cpu][0].histogram,
s->histogram_alloc_size);", which crashes with NULL pointer dereference
if s->stat_percpu[cpu] is NULL.
This commit fixes the bug by testing s->stat_percpu[cpu] for NULL before
using it.
Reported-by: Junzhe Yu <[email protected]>
Signed-off-by: Mikulas Patocka <[email protected]>
Fixes: fd2ed4d ("dm: add statistics support")
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/md/dm-stats.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=c3f211b7a277dd404b4e7d23095be964b5b46a27
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80963 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80963
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:H/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.7
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: unknown
Paranoid ActionableScore: 1
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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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