* [CVE-2026-99143][MODERATE 7.0] tracing: Keep the predicate limit separate from program capacity [ Upstream
@ 2026-10-29 4:37 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-29 4:37 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99143
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: tracing: Keep the predicate limit separate from program capacity [ Upstream
Commit: 2058a1fe791bb30fd6e4875a7ada3237076c8541
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2058a1fe791bb30fd6e4875a7ada3237076c8541
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99143
Analysis date: Thu, 29 Oct 2026 00:37:06 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A crafted tracing filter can exhaust slots mistakenly exposed as parser capacity and cause heap OOB writes when terminal predicate state is subsequently emitted.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99143 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99143
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-2026-99143 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99143 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 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:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-193;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A bounds accounting error in predicate_parse uses the allocation capacity as the predicate parsing limit. A crafted tracing filter can consume slots reserved for terminal TRUE and FALSE entries and cause out of bounds accesses to kernel heap arrays, providing at least a kernel crash and a plausible memory corruption primitive. For the CVSS the PR:L paranoid value reflects deployments where tracefs filter control is delegated to an untrusted local service or tracing group, while default systems normally restrict this interface to an administrator. Confidentiality and integrity impact are plausible but not proven because the available evidence does not establish a controlled arbitrary read or write primitive. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 7.8 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 ActionableScore threshold rule 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_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 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 TRACE SIMPLEFIX LEAK LINUS KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 3.
* Conservative score: 5. Manual-review safety floor raises 3 -> 5 because the patch establishes an attacker-influenced heap out-of-bounds write primitive.
* Raw paranoid score: 3.
* Paranoid score: 5. No additional speculative confidentiality, integrity, or privilege-escalation points.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 — Strong corruption primitive: `nr_preds` was increased by two for allocation and then incorrectly reused as the parsing limit. Crafted predicates can consume the reserved entries, after which parser/terminal-entry population accesses heap arrays beyond their allocation.
* +1 — Plausible kernel crash/strong DoS from heap-array OOB writes.
* +0 — Allocation/bounds invariant is not scored separately because it is the same defect as the OOB write.
* +0 — No privilege penalty: host-admin-only triggering is not positively established.
* +0 — No local-unprivileged bonus: the hints mention possible delegated tracefs access, but do not establish such access for the complete trigger.
* +0 — No arbitrary target, arbitrary payload, controlled adjacent victim, disclosure, or LPE is shown.
* +0 — No additional availability point; it would duplicate the same possible crash.
* B5-R does not apply: no retry/re-entry sequence or retry-accumulated index is shown. This is a direct predicate-limit/capacity accounting defect.
* B4-PENDING does not apply because no authorization decision changes from DENY to ALLOW.
3. Reachability analysis
The input is a crafted tracing filter reaching `predicate_parse()`. The actor can materially influence predicate count and contents, but the supplied evidence does not establish whether ordinary users, a delegated tracing service, or only a host administrator can write the affected tracefs filter. No namespace-scoped capability chain, special hardware, prior setup, or timing race is demonstrated. Accordingly, both effective host-admin requirement and namespace-scoped reachability remain unknown.
4. Primitive and severity reading
The primitive is a heap OOB write into parser program/inversion arrays caused by using allocation capacity as the accepted predicate limit. It is not a UAF, cleanup-only stale access, or retry-accumulated B5-R case. The shown consequence is bounded sequential corruption immediately beyond allocated arrays with plausible kernel failure. Arbitrary write, named adjacent-object corruption, confidentiality impact, persistent integrity impact, and privilege escalation remain unproven.
This is CLASS_A because an attacker-shaped predicate stream drives a confirmed heap bounds violation involving writes. ImportantCandidate is YES and automatic downgrade is disallowed because exploit leverage of the concrete heap overwrite requires manual analysis even though Important severity itself is not proven.
5. One-sentence report phrase
A crafted tracing filter can exhaust slots mistakenly exposed as parser capacity and cause heap OOB writes when terminal predicate state is subsequently emitted.
6. Manual review advice
MANUAL CHECK REQUIRED
Determine tracefs permission/delegation exposure and inspect the exact OOB write width, contents, and adjacent slab objects.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: tracing: Keep the predicate limit separate from program capacity [ Upstream
Commit: 2058a1fe791bb30fd6e4875a7ada3237076c8541
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2058a1fe791bb30fd6e4875a7ada3237076c8541
Changed files:
kernel/trace/trace_events_filter.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=2058a1fe791bb30fd6e4875a7ada3237076c8541
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99143 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99143
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:L/PR:H/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7.8
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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