[CVE-2026-98778][MODERATE 7.0] binder: fix is_failure flag for superseded transaction cleanup

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-98778
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: binder: fix is_failure flag for superseded transaction cleanup
Commit: 60a9f7323ae7318a7cce0d387c318da24f1e8726
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=60a9f7323ae7318a7cce0d387c318da24f1e8726
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98778
Analysis date: Sat, 24 Oct 2026 09:45:18 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
Binder cleanup of a superseded undelivered FDA transaction can reinterpret attacker-influenced stale values as target-process descriptor numbers and close unrelated live descriptors.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98778 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98778

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 7.0
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-2026-98778	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98778 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	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:L/A:H';CWE-404;*CWE-664;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.3';DESCR 'A logic and resource cleanup error in Binder handles a superseded TF_UPDATE_TXN transaction as if it had already been delivered. BINDER_TYPE_FDA cleanup can therefore interpret stale attacker influenced buffer values as file descriptor numbers and close unrelated descriptors in the target process. For the CVSS the PR:L value is used because exploitation requires a local process with permission to communicate with the relevant Binder object. AC:H reflects the need to supersede an undelivered asynchronous transaction and make stale values correspond to live target descriptors. The demonstrated primitive is cross process descriptor closure rather than memory corruption. It can disrupt a target service and may affect its resource state, but the patch does not establish information disclosure, arbitrary memory access, or privilege escalation. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.3 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 LOW to MODERATE_KPANIC because the manual review requirement was applied. 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 has no review artifact for this run. Exact triggered rule markers were INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK. The independent weaker Aegis shadow evaluated CVSS 3.6 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	SIMPLEFIX LINUS  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=CONFIRMED
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 5.
* Conservative score: 5; no floor or cap applied.
* Raw paranoid score: 5.
* Paranoid score: 5; stronger memory-corruption or privilege-escalation effects are unsupported.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Strong attacker-influenced semantic reinterpret: an undelivered `BINDER_TYPE_FDA` payload is incorrectly treated as containing installed target-process FD numbers.
* +1 Local below-host-admin trigger: supplied evidence identifies a local process with permission to communicate through the relevant Binder object; host UID 0 is not required.
* +1 Cross-process resource-boundary impact: cleanup closes descriptors belonging to the target process rather than resources owned by the sender.
* +1 Integrity impact: unrelated live descriptors in the target are actively closed.
* +1 Practical chain: superseded undelivered async transaction → stale FDA values → `binder_deferred_fd_close()` → target descriptor closure.
* -1 Hard trigger conditions: exploitation requires superseding an undelivered async transaction and arranging stale values that identify live target descriptors.

Not awarded: heap corruption, UAF, arbitrary write, disclosure, LPE, host-kernel panic, protected-file access, or an additional availability point. The target service may be disrupted, but host-wide fatal DoS is not established. B5-R and B3-PENDING do not apply.

3. Reachability analysis

The evidenced attacker is a local, below-host-admin Binder client with access to the relevant Binder object. The attacker must produce a pending asynchronous `TF_UPDATE_TXN` transaction and supersede it before delivery. Binder object access is an IPC-policy prerequisite, not a namespace capability or host-administrator requirement. No special hardware, boot option, or separate vulnerability is identified. Trigger complexity is high because transaction timing and stale FD-number correspondence must align.

4. Primitive and severity reading

The exact primitive is an attacker-influenced cross-process descriptor close. Passing `is_failure=false` makes cleanup interpret never-fixed-up buffer contents as installed descriptor numbers; the kernel then consumes those numbers in `binder_deferred_fd_close()`. This is active resource-state mutation, not a stale-pointer UAF or heap overwrite.

It is CLASS_A because the semantic mismatch directly causes unauthorized operations on another process’s live resources. The shown effect is descriptor closure and possible target-service disruption. Arbitrary resource access, confidentiality loss, privilege escalation, and kernel memory corruption remain unproven.

This is not an authorization-decision bypass: no mandatory guard is shown changing DENY to ALLOW, so B4 pending review is inapplicable. ImportantCandidate is YES and automatic downgrade is disallowed because a concrete cross-process integrity primitive survives beyond a crash-only interpretation.

5. One-sentence report phrase

Binder cleanup of a superseded undelivered FDA transaction can reinterpret attacker-influenced stale values as target-process descriptor numbers and close unrelated live descriptors.

6. Manual review advice

MANUAL CHECK REQUIRED

Review target-service exposure, Binder policy reachability, descriptor-number influence, and whether closure of security-sensitive service descriptors creates stronger effects.

7. Call-site confidence

Call-site confidence: medium

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

Patch: binder: fix is_failure flag for superseded transaction cleanup
Commit: 60a9f7323ae7318a7cce0d387c318da24f1e8726
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=60a9f7323ae7318a7cce0d387c318da24f1e8726

Commit description:

When a TF_UPDATE_TXN transaction supersedes a pending async transaction,
binder_release_entire_buffer() is called with is_failure=false. Since the
superseded transaction was never delivered, binder_apply_fd_fixups() was
never called and no fds were installed in the target process.

With is_failure=false, the BINDER_TYPE_FDA cleanup handler interprets
stale buffer contents as installed fd numbers and passes them to
binder_deferred_fd_close(), closing unrelated file descriptors.

Pass is_failure=true since the transaction was never delivered to the
target, matching the semantics of all other undelivered-transaction
cleanup paths.

Fixes: 9864bb4 ("Binder: add TF_UPDATE_TXN to replace outdated txn")
Cc: stable <stable@kernel.org>
Signed-off-by: Tomer Pomeranc <tomerpo@gmail.com>
Acked-by: Carlos Llamas <cmllamas@google.com>
Link: https://patch.msgid.link/20260812195316.259136-3-tomerpo@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/android/binder.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=60a9f7323ae7318a7cce0d387c318da24f1e8726

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

The original Linux kernel CVE announcement for CVE-2026-98778 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98778

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:N/I:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H
  The Best / paranoid CVSS score: 5.3

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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).