[CVE-2026-72083][IMPORTANT] scsi: target: core: Fix iSCSI ISID use-after-free in REGISTER AND MOVE

[CVE-2026-72083][IMPORTANT] scsi: target: core: Fix iSCSI ISID use-after-free in REGISTER AND MOVE

[AL-KERNEL]

CVE: CVE-2026-72083
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: scsi: target: core: Fix iSCSI ISID use-after-free in REGISTER AND MOVE
Commit: 7d56f5c868d92c9d504a34a3ea450bce481c7f63
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7d56f5c868d92c9d504a34a3ea450bce481c7f63
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72083
Analysis date: Sat, 15 Aug 2026 04:43:57 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A network-reachable use-after-free read in the Linux SCSI iSCSI target PR OUT REGISTER AND MOVE path can dereference an ISID pointer after the mapped parameter list is unmapped, causing at least remote kernel crash DoS and requiring manual review for possible limited C/I impact.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-72083 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72083

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-72083	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-825;*CWE-664;Other CVSS 'AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '8.6';DESCR 'A use after free read exists in the SCSI target PR OUT REGISTER AND MOVE path because an iSCSI ISID pointer can alias the mapped parameter list and remain in use after transport_kunmap_data_sg() tears down the mapping. A remote iSCSI initiator can trigger this with a parameter list larger than one page, where the buffer may be mapped with vmap() and later unmapped with vunmap(), leaving iport_ptr as a stale kernel virtual pointer used by strcmp and reservation lookup or allocation logic. For the CVSS the PR:N is used for the paranoid score because an exposed iSCSI target may accept a network initiator without additional local privileges, while authenticated storage deployments may be better represented by PR:L. The issue is network reachable in environments where the iSCSI target port is reachable from an attacker controlled initiator. Impact is at least denial of service via kernel crash and in worst case may allow limited confidentiality or integrity impact due to stale pointer based parsing in kernel target code, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)	YES	OOB ERRORPATH UAF 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2
  The affected path is in the iSCSI SCSI target command handling path and can be reached by an iSCSI initiator that can send PR OUT REGISTER AND MOVE commands.

* Memory corruption, weak/indirect corruption candidate: +1
  The bug is an explicit stale pointer / use-after-free read of `iport_ptr` after `transport_kunmap_data_sg()` tears down the mapped parameter buffer. It is read-only in the shown path, so this is not treated as a strong overwrite primitive.

* Real lifetime corruption: +1
  `iport_ptr` aliases a mapped PR OUT parameter list and remains live after the mapping is destroyed by `vunmap()`.

* Reliable kernel crash / strong DoS: +1
  Subsequent dereferences in `strcmp()`, reservation lookup, or allocation logic can fault on an unmapped kernel virtual address.

* Important filesystem/storage path: +1
  This affects Linux SCSI target persistent reservation handling over iSCSI, a storage protocol path with operationally important availability impact.

Paranoid additional signals:

* Confidentiality impact plausible: +1
  In a worst still-defensible interpretation, stale pointer based reads from a reused or invalid kernel virtual mapping could expose limited unintended data, although no direct leak primitive is demonstrated.

* Integrity impact plausible: +1
  The stale pointer influences reservation lookup and registration logic, so limited integrity impact is plausible in triage, but not proven as arbitrary write or privilege escalation.

## 3. Reachability analysis

An attacker must be able to act as an iSCSI initiator against an affected Linux SCSI target and send a crafted PR OUT REGISTER AND MOVE command with a parameter list larger than one page. No local code execution on the target host is required if the iSCSI target portal is reachable over the network.

In typical deployments, iSCSI targets are usually placed on isolated storage or data-center networks and may require initiator ACLs or authentication. That reduces Internet-scale exposure but does not remove network-triggerability in environments where an attacker has access to the storage network or a permitted initiator identity.

Namespaces and containers are not the primary factor here. The relevant boundary is network/storage access to the iSCSI target service, not local Linux namespace privileges.

Call-site confidence: high. The commit message identifies the stale pointer users after unmap, including `strcmp()`, `__core_scsi3_locate_pr_reg()`, and `core_scsi3_alloc_registration()`.

## 4. Severity interpretation

This is not an ordinary Moderate cleanup because the patch fixes a concrete lifetime bug in a network-reachable kernel storage target path. The realistic impact is remote denial of service through a kernel fault or crash.

Theoretical impact beyond DoS is weaker but not ignorable. The primitive is a stale pointer read, not a demonstrated write-after-free, object replacement, callback hijack, or arbitrary memory corruption. Therefore the conservative score stays in Actionable Moderate territory, while the paranoid score reaches Strong Important candidate due to network reachability plus explicit UAF/lifetime corruption in kernel target code.

## 5. One-sentence report phrase

A network-reachable use-after-free read in the Linux SCSI iSCSI target PR OUT REGISTER AND MOVE path can dereference an ISID pointer after the mapped parameter list is unmapped, causing at least remote kernel crash DoS and requiring manual review for possible limited C/I impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a network-reachable UAF/lifetime bug in kernel storage target code. The demonstrated impact is DoS, but the stale pointer is later used in reservation lookup and allocation logic, so it should not be auto-closed without manual review.

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UPSTREAM PATCH SUMMARY
======================================================================

Patch: scsi: target: core: Fix iSCSI ISID use-after-free in REGISTER AND MOVE
Commit: 7d56f5c868d92c9d504a34a3ea450bce481c7f63
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7d56f5c868d92c9d504a34a3ea450bce481c7f63

Commit description:

core_scsi3_emulate_pro_register_and_move() maps the PERSISTENT RESERVE OUT
parameter list with transport_kmap_data_sg() and parses the destination
TransportID with target_parse_pr_out_transport_id(). For an iSCSI
TransportID (FORMAT CODE 01b), iscsi_parse_pr_out_transport_id() returns
the ISID in iport_ptr as a raw pointer into that mapped buffer.

The function then unmaps the buffer with transport_kunmap_data_sg() before
dereferencing iport_ptr in strcmp(), __core_scsi3_locate_pr_reg() and
core_scsi3_alloc_registration(). When the parameter list spans more than
one page (PARAMETER LIST LENGTH > 4096), transport_kmap_data_sg() uses
vmap() and transport_kunmap_data_sg() does vunmap(), so the kernel virtual
address backing iport_ptr is torn down and every subsequent dereference is
a use-after-free read of the unmapped region.

Keep the parameter list mapped until iport_ptr is no longer needed: drop
the early transport_kunmap_data_sg() and unmap once on the success path,
right before returning. The error paths already unmap through the existing
"if (buf) transport_kunmap_data_sg(cmd)" at the out: label, which now runs
on every post-map error exit because buf is no longer cleared early. Only
reads of the mapping happen while spinlocks are held; the map and unmap
calls remain outside any lock. The sibling caller
core_scsi3_decode_spec_i_port() already uses the buffer before unmapping it
and is left unchanged.

Fixes: 4949314 ("target: Allow control CDBs with data > 1 page")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: David Disseldorp <ddiss@suse.de>
Link: https://patch.msgid.link/20260610042245.35473-1-hexlabsecurity@proton.me
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/target/target_core_pr.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=7d56f5c868d92c9d504a34a3ea450bce481c7f63

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DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-72083 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72083

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:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 8.6

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: 8

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).