* [CVE-2026-98479][IMPORTANT] scsi: libiscsi_tcp: Check the data direction of a Data-In PDU
@ 2026-10-24 14:05 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-24 14:05 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98479
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: scsi: libiscsi_tcp: Check the data direction of a Data-In PDU
Commit: 79991b770fc3685b1d5cf805b659a879edd19931
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=79991b770fc3685b1d5cf805b659a879edd19931
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98479
Analysis date: Sat, 24 Oct 2026 10:05:14 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A malicious connected iSCSI target can inject controlled bytes into an initiator WRITE command’s caller or page-cache pages by sending a Data-In PDU for its ITT.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98479 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98479
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-2026-98479 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-98479 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT IMPORTANT AEGIS_AS=6 LEGACY=IMPORTANT RESULT=SAME (final reconciliation agrees; DECISION: both IMPORTANT) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H';*CWE-20;CWE-841;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L';BEST CVSS score: '8.1';DESCR 'The iSCSI initiator accepted a Data-In PDU for a WRITE command and copied target supplied bytes into the command scatterlist. A malicious or compromised target can therefore modify an O_DIRECT caller buffer or silently replace page cache data while pwrite and fsync still report success. The primitive is a bounded write into valid command pages rather than an OOB write or UAF, so direct kernel code execution and information disclosure are not established. For the CVSS the PR:N value is used because the attacker needs no privilege on the initiator after controlling the connected iSCSI target or an equivalent authenticated session endpoint. AV:A reflects that exploitation requires an established storage network relationship rather than arbitrary Internet reachability. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 8.1 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. final reconciliation stage IMPORTANT to IMPORTANT because KP specialist did not establish a qualifying panic. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 6.5 and ActionableScore 6 with primitive class CLASS_A and manual review REQUIRED. Its independently reconciled impact was IMPORTANT. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE REMOTE WRITE OOB NETWORK HARDWARE LINUS TEST INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC_UNSUPPORTED_REMOVED - - checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 4.
* Conservative score: 5. Applied the manual-review safety floor for a controlled write into active caller/page-cache storage: 4 -> 5.
* Raw paranoid score: 4.
* Paranoid score: 5. No additional speculative impact awarded; the same safety floor applies.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 controlled page-cache/process-memory write: target-selected Data-In bytes are copied into the scatterlist of a WRITE command. This counts once as the strong write primitive.
* +1 integrity impact: O_DIRECT caller memory is modified, while buffered writes silently acquire target-supplied page-cache contents.
* +1 practical chain: the commit reports successful `pwrite()`/`fsync()` followed by reads returning the injected bytes.
* No OOB/UAF, arbitrary target, cross-file permission bypass, disclosure, LPE, or kernel crash is shown.
* No extra availability point: the patch establishes silent corruption, not panic or host-wide failure.
* B5-R does not apply: there is no retry-accumulated heap OOB write.
* B4 does not apply: the direction check is protocol/type validation, not an authorization DENY-to-ALLOW guard.
3. Reachability analysis
A malicious or compromised iSCSI target can emit the malformed Data-In PDU over an established initiator session. Host-side iSCSI configuration is prior privileged setup, but the actor exercising the flaw afterward needs neither host UID 0 nor host-administrator powers. This is not arbitrary Internet reachability and receives no generic remote bonus. Namespace capabilities and special hardware are not involved; no race is required.
4. Primitive and severity reading
The primitive is a bounded, target-payload-controlled write into valid pages belonging to the selected outstanding WRITE command. It affects active caller memory or page-cache state and is later consumed by userspace/filesystem reads. This is CLASS_A because actual controlled data corruption is demonstrated, although destination choice remains constrained by the command scatterlist. Arbitrary kernel memory write, protected-file overwrite, persistence beyond cache/storage semantics, and code execution remain unproven. ImportantCandidate is retained because a storage trust-boundary peer can silently corrupt initiator-owned active data; automatic downgrade would discard that demonstrated integrity primitive.
5. One-sentence report phrase
A malicious connected iSCSI target can inject controlled bytes into an initiator WRITE command’s caller or page-cache pages by sending a Data-In PDU for its ITT.
6. Manual review advice
MANUAL CHECK REQUIRED
Confirm deployment exposure and whether affected write buffers can contain data crossing stronger process, file-ownership, or storage trust boundaries.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: scsi: libiscsi_tcp: Check the data direction of a Data-In PDU
Commit: 79991b770fc3685b1d5cf805b659a879edd19931
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=79991b770fc3685b1d5cf805b659a879edd19931
Commit description:
The Data-In branch of iscsi_tcp_hdr_dissect() resolves the ITT to a task
and copies the PDU's data segment into that command's scatterlist without
asking whether the command was reading. iscsi_tcp_r2t_rsp() in the same
file does ask, and rejects an R2T for a command that is not DMA_TO_DEVICE.
A target that answers a WRITE command's ITT with a Data-In therefore has
the initiator write target-supplied bytes into the pages that write was
about to send. Those are the caller's own pinned pages for an O_DIRECT
write, and page cache pages for a buffered one.
Observed against a test target that emits one 512-byte Data-In naming a 128
KB write's ITT, after the R2T for that write. With O_DIRECT the caller's
buffer ends up holding 512 bytes of the target's data while pwrite()
returns 131072. Buffered is quieter: pwrite() and fsync() both succeed,
nothing is logged, and reading those blocks back returns the target's bytes
out of the page cache without a command going on the wire.
Check the direction before using the scatterlist, the way the R2T path
already does.
Cc: [email protected]
Signed-off-by: Yehyeong Lee <[email protected]>
Reviewed-by: Mike Christie <[email protected]>
Link: https://patch.msgid.link/[email protected]
Fixes: a081c13 ("[SCSI] iscsi_tcp: split module into lib and lld")
Signed-off-by: Martin K. Petersen (Oracle) <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/scsi/libiscsi_tcp.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=79991b770fc3685b1d5cf805b659a879edd19931
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98479 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98479
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:H/A:L
The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
The Best / paranoid CVSS score: 8.1
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: unknown
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: IMPORTANT
KPANIC detected for this report: NO
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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