* [CVE-2026-98534][MODERATE 7.0] ipe: fix use-after-free when auditing a newly loaded policy [ Upstream
@ 2026-10-23 23:54 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-23 23:54 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98534
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ipe: fix use-after-free when auditing a newly loaded policy [ Upstream
Commit: b72d6c72b4bfbc021e8e127fa13e0f27d09be737
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b72d6c72b4bfbc021e8e127fa13e0f27d09be737
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98534
Analysis date: Fri, 23 Oct 2026 19:54:46 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A race between IPE policy publication and concurrent policyfs deletion can free a newly loaded policy before audit processing finishes, causing a local active-object use-after-free with kernel crash potential and unresolved post-reuse consequences.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98534 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98534
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.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98534 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98534 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 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:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in IPE policy loading can cause ipe_audit_policy_load() to access a policy after a concurrent policyfs deletion has freed it. The policy becomes visible after ipe_new_policyfs_node() publishes it, but the original code released the directory inode lock before auditing the successful load. A second local execution context can delete the published policy during this interval, resulting in a use after free and a possible kernel crash. The issue is not network reachable and requires local access to the IPE policy management interface. For the CVSS the PR:L in the paranoid score represents a delegated policy manager, reduced capability root, or service account that can load and remove IPE policies without having unrestricted control over the host. Reliable triggering also requires winning a race, therefore AC:H is appropriate. Impact is at least a local denial of service via kernel crash. In the worst case, reuse of the freed policy object may create confidentiality or integrity impact, but privilege escalation is not proven and requires manual source level review. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 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. KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because FD false positive review allowed a downgrade. 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 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 4 with primitive class CLASS_B 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 UAF LINUS KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 4
* Raw paranoid score: 4
* Paranoid score: 5
* Conservative floor applied: 3 -> 4 under the real UAF floor because a freed active policy is actually consumed and host-admin-equivalent privilege is not positively established by the supplied context.
* Paranoid floor applied: 4 -> 5 because the stronger defensible interpretation involves repeatable policy publication and deletion while structured policy state is consumed by audit processing.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Conservative signals:
* +2 Real UAF. `ipe_new_policyfs_node()` publishes the policy and releases the inode lock. Concurrent deletion can free the exact policy while `ipe_audit_policy_load()` still uses it.
* +1 Realistic kernel crash. Audit processing dereferences an object whose lifetime may already have ended. A stale pointer fault is a credible consequence.
* +0 Race penalty. The commit establishes a race but does not establish that the timing is one-shot, exceptionally narrow, or externally uncontrollable.
* +0 Privilege penalty. Access to IPE policy management is required, but the supplied code does not establish whether the complete load and delete sequence necessarily requires host-admin-equivalent power.
Paranoid additional signal:
* +1 Attacker-influenced lifetime manipulation. A policy-management actor that can perform both operations can repeatedly publish and delete policy objects while auditing is active. This interpretation is plausible but depends on policyfs permissions not shown in the patch.
Floor rationale:
* The stale object is an active `ipe_policy`, not fixed stale storage.
* The stale use enters audit processing rather than an immediate destructor-only cleanup.
* Policy fields are consumed after publication and possible deletion.
* Exact audit field consumption and reclaim behavior remain unresolved, so the score is preserved at 5 for review rather than promoted to Class A.
Not awarded:
* Controlled reclaim is not demonstrated.
* An arbitrary or directed kernel write is not demonstrated.
* Structured stale-object leverage is not separately awarded because the supplied code does not show which fields `ipe_audit_policy_load()` consumes after reuse.
* Confidentiality and integrity points are not awarded merely because freed memory might be reused.
* Privilege escalation is not demonstrated.
* No concrete repeated release or refcount mutation occurs. The stale operation is an audit-time dereference, not a second `put`, `free`, or refcount decrement.
* Reliable crash and availability are counted only once.
* Remote reachability is not established.
* No authorization decision changes from DENY to ALLOW. B4-PENDING does not apply.
* NEW52 B5-R does not apply because no retry-accumulated heap OOB write exists.
* NEW53 B3-PENDING does not apply because no shared-backing write exists.
* V32 through V34 do not apply because no checksum metadata or SKB write is involved.
Repeated-release checks:
* First release can end lifetime: deletion can free the policy, but this is not a visible first release followed by another release in the audited path.
* Exact reference survives: yes, `new_policy()` retains `p` and passes it to audit after publication.
* Second lifetime or refcount mutation: no. The second operation consumes the stale policy but does not perform a demonstrated lifetime mutation.
* Concrete repeated release bonus: not awarded.
* Paranoid repeated-refcount bonus: not awarded.
* Repeated-release FLOOR 5 condition: not used.
3. Reachability analysis
The trigger requires one execution context to load and publish a policy while another deletes it before audit processing completes. This is local and not network reachable.
The supplied patch does not show the securityfs file modes, capability checks, ownership rules, or whether policy-management rights can be delegated. Consequently, host-admin privilege cannot be positively marked YES, but below-host-admin reachability also cannot be marked NO. `HostAdminRequired=UNKNOWN` is therefore appropriate.
The complete sequence is not shown to be available inside attacker-created user or security namespaces. `NamespaceScopedPrivilege=UNKNOWN` is used rather than assuming namespace reachability.
IPE must be enabled and a userspace signed policy must reach the successful publication path because the moved audit call is conditioned on `p->pkcs7`. No special hardware is required. The race appears repeatable if the same actor can repeatedly load and delete policies, but that actor model requires verification against the complete policyfs permission path.
4. Primitive and severity interpretation
The exact primitive is a real use-after-free of `struct ipe_policy`. The directory inode lock protects publication and deletion, but the vulnerable code released that lock before auditing. Deletion could therefore end the policy lifetime while `new_policy()` retained and used the stale pointer.
This is an active structured-object UAF. It is not fixed stale storage and is not merely passive metadata. However, the supplied context only establishes stale use by the audit path. It does not establish controlled replacement, callback dispatch, arbitrary read or write, disclosure, or credential modification.
This is category A from the cleanup distinction only in the descriptive sense of an ordinary stale dereference, not the prompt's Primitive Class A. There is no category B repeated lifetime mutation because audit does not perform a second release or refcount operation.
The demonstrated consequence is UAF with plausible kernel crash or audit-state misuse. A stronger consequence through slab reuse is unresolved rather than demonstrated. The primitive is therefore CLASS_B, not CLASS_A.
`ImportantCandidate=YES` preserves the active-object lifetime issue for source-level review because policy creation, deletion, stale audit consumption, and possible repeated triggering form a concrete unresolved lifetime chain. It does not assert proven privilege escalation or Important severity.
`AutoDowngradeAllowed=NO` is selected because automatically reducing the issue to an ordinary crash would discard unresolved active-policy field consumption and the possible repeated publication/deletion surface. Manual review should determine whether audit processing follows nested pointers, exposes stale data, or permits meaningful post-reuse behavior.
5. One-sentence report phrase
A race between IPE policy publication and concurrent policyfs deletion can free a newly loaded policy before audit processing finishes, causing a local active-object use-after-free with kernel crash potential and unresolved post-reuse consequences.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Review `ipe_audit_policy_load()`, `ipe_free_policy()`, the policyfs deletion path, allocation cache reuse, nested policy fields consumed by auditing, and the exact permissions required to perform both policy load and deletion.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: ipe: fix use-after-free when auditing a newly loaded policy [ Upstream
Commit: b72d6c72b4bfbc021e8e127fa13e0f27d09be737
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b72d6c72b4bfbc021e8e127fa13e0f27d09be737
Changed files:
security/ipe/fs.c
security/ipe/policy_fs.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=b72d6c72b4bfbc021e8e127fa13e0f27d09be737
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98534 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98534
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:H/UI:N/S:U/C:N/I:N/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: 4
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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