* [CVE-2026-90008][IMPORTANT] scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame
@ 2026-09-16 18:41 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-16 18:41 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90008
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame
Commit: 4bb34769ef44ab3770b89e4055de6af4a458bec9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4bb34769ef44ab3770b89e4055de6af4a458bec9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90008
Analysis date: Wed, 16 Sep 2026 14:41:12 -0400
ActionableScore: 7
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate
Manual review required: YES
Summary:
An out-of-bounds write in megaraid_sas PRP list construction can overrun the command DMA frame during large NVMe I/O, causing kernel crash or corruption of neighbouring in-flight command metadata.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90008 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90008
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: IMPORTANT
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-2026-90008 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-90008 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-119;CWE-131;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An out-of-bounds write can occur in megaraid_sas when megasas_make_prp_nvme builds an NVMe PRP list in cmd sg_frame without bounding the number of entries against the DMA pool buffer size. Large I/O requests on NVMe drives with a large MDTS can require more PRP entries than the chain frame can hold, causing the list to run past the end of the frame. If the next page is unmapped this causes a kernel page fault and denial of service. If the adjacent DMA pool entry is mapped, the overrun can silently corrupt another in-flight command PRP list, which makes this a memory corruption candidate rather than a pure crash bug. For the CVSS the PR:L is used because a local user able to generate large file or block I/O may be able to reach the vulnerable path without full administrative privileges. The issue is not network reachable. Impact is at least local denial of service and in the paranoid case may include confidentiality and integrity impact due to corruption of DMA command metadata.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate (with actual score 7) SKIP CVE-2026-90008 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE DANGER DMAorINTERRUPT HARDWARE KPANIC MEMORY KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=7
ActionableScoreLower=6
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
## 1. ActionableScore
* Raw conservative score: 6
* Conservative score: 6
* Raw paranoid score: 7
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate**::
No floor or cap was applied.
## 2. Signal breakdown
Conservative signals:
* +2 Strong corruption primitive: `megasas_make_prp_nvme()` can write PRP entries past `cmd->sg_frame`, which is a fixed DMA pool buffer.
* +1 Reliable kernel crash / strong DoS: the report shows a supervisor write page fault in kernel mode when the overrun reaches an unmapped page.
* +1 Local below-host-admin trigger: large file or block I/O can realistically reach the PRP construction path once the affected storage stack exists.
* +1 Important storage path: this is in the SCSI/NVMe storage command submission path and can affect in-flight I/O metadata.
* +1 DMA descriptor corruption: the commit explicitly states that if the next page is mapped, the overrun can corrupt a neighbouring pool entry, another in-flight command's PRP list.
Paranoid additional signal:
* +1 Local high-control data-plane aspect: a local user can influence I/O size, alignment, and request pattern, which affects PRP list length and the chance of hitting adjacent in-flight command metadata.
Non-awarded signals:
* RealUAF not awarded: this is an out-of-bounds write, not a stale lifetime use.
* Arbitrary kernel write not awarded: target selection is constrained to adjacent DMA pool memory.
* Controlled reclaim not demonstrated.
* Remote reachability not established.
* Race/timing penalty not applied: this is not a timing race.
* Hardware penalty not applied: megaraid_sas hardware is device-specific but not proven rare or physical-attacker-only.
* Extra availability point not awarded: the observed crash is already counted.
* Confidentiality and integrity are not separately scored as demonstrated consequences, but the active DMA metadata corruption keeps this in CLASS_A and requires review.
## 3. Reachability analysis
The vulnerable path is reached through normal block I/O submitted to an NVMe device behind `megaraid_sas`. The trigger depends on a device reporting a large MDTS and on large enough requests after the block layer default increased to 4 MiB.
A host administrator is needed to have the affected hardware and storage stack configured, but the complete runtime trigger does not necessarily require host-admin privileges. A normal local user with access to files on the affected filesystem may generate large reads or writes that enter this path. Direct raw block-device access would be more privileged, but file I/O is enough to keep `HostAdminRequired=NO`.
This is not namespace-scoped. No network trigger is established. No special race is required. The main environmental prerequisite is affected MegaRAID/NVMe hardware and a request size large enough to exceed the PRP chain frame capacity.
## 4. Primitive and severity interpretation
The exact primitive is an out-of-bounds kernel write while building an NVMe PRP list into `cmd->sg_frame`. The buffer size is `instance->max_chain_frame_sz`, but the old limit used firmware-derived `max_io_size` without ensuring that the PRP entries fit in the chain frame.
This is active DMA command metadata, not passive bookkeeping. The commit explicitly distinguishes two outcomes: immediate kernel page fault when the overrun reaches unmapped memory, or silent corruption of a neighbouring DMA pool entry when it is mapped. The neighbouring entry may be another in-flight command's PRP list, making this an active descriptor corruption primitive.
PrimitiveClass is CLASS_A because the patch establishes a real OOB write into kernel DMA command metadata with possible corruption of another active command descriptor. RealUAF is NO. The demonstrated consequence is kernel crash. The unresolved consequence is whether corrupted PRP metadata can be steered into stronger integrity or confidentiality impact through misdirected device I/O. That possibility is not proven as arbitrary read/write, but it is strong enough to require manual review and prevent automatic downgrade.
ImportantCandidate=YES because this is not a pure DoS-only NULL dereference or resource leak. AutoDowngradeAllowed=NO because automatic closure would discard a concrete kernel OOB write affecting active DMA/storage metadata.
Likely operational severity: Strong Important candidate, especially on systems where untrusted local users can generate large I/O on affected storage.
## 5. One-sentence report phrase
An out-of-bounds write in megaraid_sas PRP list construction can overrun the command DMA frame during large NVMe I/O, causing kernel crash or corruption of neighbouring in-flight command metadata.
## 6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: concrete OOB write into DMA command metadata is established, and the commit explicitly notes silent corruption of another in-flight PRP list.
## 7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame
Commit: 4bb34769ef44ab3770b89e4055de6af4a458bec9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4bb34769ef44ab3770b89e4055de6af4a458bec9
Commit description:
megasas_make_prp_nvme() builds a command's PRP list in cmd->sg_frame, a
DMA pool buffer of instance->max_chain_frame_sz bytes, spending one
entry per NVMe page of the transfer plus one per page of the buffer for
the chain pointer. The loop runs until the transfer is described and
never checks the buffer bound.
max_hw_sectors comes straight from the MDTS the firmware reports for the
drive. On drives with a large MDTS the only thing keeping the list
inside the buffer was the block layer default of 1280 KiB, which needs
320 entries, which fit into a 4 KiB frame as that holds 512. But since
commit 9b8b848 ("block: Increase BLK_DEF_MAX_SECTORS_CAP") that
default is 4 MiB, and such a transfer needs 1025 entries, so the list
runs a full page past the end of the frame:
sd 1:0:1:0: [sdb] tag#630 page boundary ptr_sgl: 0x00000000ba62d13f
BUG: unable to handle page fault for address: ff663bcb81e7c000
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
RIP: 0010:megasas_build_and_issue_cmd_fusion+0xeaa/0x1870 [megaraid_sas]
If the page after the frame happens to be mapped, the overrun does not
fault but silently corrupts the neighbouring pool entry, which is
another in-flight command's PRP list.
Cap max_hw_sectors at what the chain frame can describe, less one page
for transfers that do not start on a page boundary and so need one entry
more. This is the megaraid_sas counterpart of commit 04631f5
("scsi: mpt3sas: Limit NVMe request size to 2 MiB"), but derives the
limit from max_chain_frame_sz rather than hardcoding it.
Cc: [email protected]
Fixes: 9b8b848 ("block: Increase BLK_DEF_MAX_SECTORS_CAP")
Reported-by: Lukasz Magiera <[email protected]>
Closes: https://lore.kernel.org/all/GPhsSM0vkgyIrs0DIZ62qeUZX7X4RxwQXVKiuvMx-lHQVSPDxpztUyQOGS0xikqvJ-Z94hMV-dW_5KN_0CX2hsfV7kTf_t0MTf6vdAAaSEc=@magik.net/
Reported-by: Mira Limbeck <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Suggested-by: Martin K. Petersen <[email protected]>
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Thomas Lamprecht <[email protected]>
Closes: https://lore.kernel.org/linux-scsi/[email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Martin K. Petersen (Oracle) <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/scsi/megaraid/megaraid_sas_base.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=4bb34769ef44ab3770b89e4055de6af4a458bec9
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90008 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90008
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:L/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/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: 6
Paranoid ActionableScore: 7
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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT
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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