* [CVE-2026-97565][MODERATE REGULAR] smb: client: reject short READ responses in CIFSSMBRead()
@ 2026-09-25 11:44 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-25 11:44 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97565
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: smb: client: reject short READ responses in CIFSSMBRead()
Commit: 0f1f77b821506a4dacab6ce7d29cf9e0c26f14cd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f1f77b821506a4dacab6ce7d29cf9e0c26f14cd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97565
Analysis date: Fri, 25 Sep 2026 07:44:31 -0400
ActionableScore: 1
ActionableScore lower bound: 0
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-2026-97565 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97565
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 REGULAR
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-2026-97565 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97565 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;*CWE-20;CWE-1284;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.1';DESCR 'The patch rejects responses shorter than read_rsp_size before dereferencing READ_RSP fields and resets nbytes on error. YES REQUIRES MANUAL CHECK because the issue is network reachable through SMB1 and contains an out-of-bounds kernel read that may have secondary effects.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) SKIP CVE-2026-97565 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE DISK SIMPLEFIX SERVERTOCLIENT LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
ActionableScoreLower=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Conservative signals:
* +1 Weak corruption/crash concern. A truncated SMB1 READ_RSP causes a concrete but limited out-of-bounds kernel read.
* -1 Legacy/non-default mode. The path requires an explicit SMB1 mount using vers=1.0, and SMB1 is not negotiated by default.
Paranoid-only signal:
* +1 Plausible kernel crash. Reading beyond the receive buffer can fault if the access crosses valid backing memory, although no actual panic or reliable crash is demonstrated.
Important non-awarded signals:
* Direct remote reachability +2 was not awarded because reaching the path requires prior explicit SMB1 mount configuration.
* Confidentiality was not awarded because no path copying adjacent kernel bytes to the server or userspace is established.
* Integrity was not awarded because there is no write, UAF, lifetime mutation, or controlled corruption primitive.
* Strong DoS was withheld from the conservative score because the visible evidence establishes an invalid read but not a reliable host crash.
* No additional availability point was awarded.
* No strong or weak LPE leverage was established.
3. Reachability analysis
A malicious or compromised SMB1 server can trigger the invalid read after the victim has explicitly mounted it with vers=1.0. The server-side attacker needs no account or privilege on the client, so HostAdminRequired is NO for the actual malformed-response trigger.
A separate privileged actor will normally have performed the mount, making prior privileged setup a prerequisite rather than an attacker privilege. The issue is therefore network-influenced but not directly network-triggerable under the scoring definition that excludes paths requiring privileged local configuration. No namespace capability is involved in the supplied path. There is no race, special hardware, or timing requirement.
4. Primitive and severity interpretation
The exact primitive is a bounded header-level out-of-bounds read from a short SMB1 response buffer. It is neither a UAF nor an active-object lifetime violation. No repeated release, refcount mutation, controlled reclaim, disclosure path, or write primitive exists in the supplied evidence.
PrimitiveClass is CLASS_C because the demonstrated behavior is invalid parsing with possible crash or DoS, without an independently useful corruption primitive. ImportantCandidate is NO because exploitation leverage beyond a possible fault is not established. AutoDowngradeAllowed is YES because unresolved Class A or Class B behavior is absent.
The practical severity is ordinary Moderate to Low-like due to the explicit legacy SMB1 mount prerequisite and the limited read primitive. Manual review remains recommended to confirm whether derived length and offset fields can influence a later copy or expose adjacent data outside the visible patch context.
5. One-sentence report phrase
A malicious SMB1 server can return a truncated READ response that causes CIFSSMBRead to parse fields beyond the receive buffer, creating a limited kernel out-of-bounds read with possible denial-of-service impact on clients explicitly mounted with vers=1.0.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Review the remaining CIFSSMBRead data-return path to determine whether out-of-bounds header values can cause disclosure, a subsequent invalid copy, or a reliable kernel crash.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: smb: client: reject short READ responses in CIFSSMBRead()
Commit: 0f1f77b821506a4dacab6ce7d29cf9e0c26f14cd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f1f77b821506a4dacab6ce7d29cf9e0c26f14cd
Commit description:
CIFSSMBRead() reads DataLengthHigh, DataLength and DataOffset out of
the READ_RSP returned by the server without first checking that a
whole READ_RSP was actually received. The length of the response is
recorded in rsp_iov.iov_len, but nothing constrains it to be at least
read_rsp_size before those fields are dereferenced.
A malicious or compromised SMB1 server can return a response shorter
than the READ_RSP header, so that parsing the header itself reads past
the end of the receive buffer. SMB1 is not negotiated by default;
reaching this code requires an explicit vers=1.0 mount.
Reject the response unless it is at least read_rsp_size bytes long.
Fixes: 1da177e ("Linux-2.6.12-rc2")
Suggested-by: Paulo Alcantara <[email protected]>
Cc: [email protected] # 6.19.x
Assisted-by: Bynario AI
Signed-off-by: Diego Oliva <[email protected]>
Reviewed-by: David Howells <[email protected]>
Signed-off-by: Paulo Alcantara <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
fs/smb/client/cifssmb.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=0f1f77b821506a4dacab6ce7d29cf9e0c26f14cd
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97565 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97565
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:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
The Best / paranoid CVSS score: 7.1
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: 0
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: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
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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