From: AL-KERNEL <[email protected]>
To: [email protected]
Subject: [CVE-2026-99247][LOW] tracing: Do not initialize tracefs work if tracing is disabled
Date: Tue, 03 Nov 2026 22:45:19 -0400 [thread overview]
Message-ID: <[email protected]> (raw)
CVE: CVE-2026-99247
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: tracing: Do not initialize tracefs work if tracing is disabled
Commit: e8665e884e076d894f3eed8b9ea28e37a6448604
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8665e884e076d894f3eed8b9ea28e37a6448604
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99247
Analysis date: Tue, 03 Nov 2026 22:45:19 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
An early trace-buffer allocation failure can leave tracing state uninitialized and cause a later tracefs worker to crash the kernel during boot.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99247 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99247
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: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-99247 LOW https://www.kernelcve.org/list/?q=CVE-2026-99247 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-665;CWE-703;BEST CVSS score: '4.1';DESCR 'A failed trace buffer allocation during early boot leaves tracing_disabled set and the global trace array events list uninitialized. The later asynchronous tracefs initialization can call __find_event_file and dereference the uninitialized list which causes a kernel Oops and may prevent the system from completing boot. For the CVSS the PR:H value reflects that reliable triggering would require control over boot configuration or similarly privileged control over the early memory environment. AC:H reflects the prerequisite allocation failure before user space starts. There is no supported remote trigger and no evidence of UAF OOB access arbitrary write information disclosure or privilege escalation. Availability impact is high because the fault can stop boot while confidentiality and integrity remain unaffected. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.1 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 4.1 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE NULLPTR INIT TRACE LEAK LINUS - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: -2.
* Conservative score: 0, after clamping the negative raw score to the minimum.
* Raw paranoid score: -2.
* Paranoid score: 0, after the same minimum-score clamp.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Reliable kernel crash/strong DoS: the documented uninitialized-list read causes an early-boot NULL-pointer Oops and may prevent boot completion.
* -2 Host-admin-equivalent trigger: reliable attacker induction requires control over boot configuration or similarly privileged control over the early memory environment.
* -1 Rare and difficult-to-reach condition: the path requires trace-buffer allocation failure before userspace starts; an ordinary runtime actor cannot instantiate it.
* No extra availability point: boot failure is the same crash consequence.
* No UAF, OOB write, attacker-controlled corruption, disclosure, authorization bypass, or integrity primitive is shown.
* B5-R does not apply: there is no heap OOB write, retry-accumulated index, attacker-influenced retry sequence, or later consumption of corrupted written state.
* B3-PENDING and B4-PENDING do not apply.
3. Reachability analysis
The prerequisite is an early-boot trace-buffer allocation failure. No remote, local-unprivileged, namespace-capability, or post-boot trigger is evidenced. Reliable attacker control would require host-administrator-equivalent influence over boot or early memory conditions. Numeric host UID 0 specifically is not established. There is no race; the difficulty comes from inducing the pre-userspace allocation failure.
4. Primitive and severity reading
The exact behavior is a read through an uninitialized global event-list head, producing a NULL-pointer dereference. This is CLASS_C crash/invalid-state behavior, not a lifetime violation or write primitive. The asynchronous worker is a later consumer of failed initialization state, but it only yields the shown invalid read and Oops. Important-grade leverage is unsupported, so automatic downgrade is safe.
5. One-sentence report phrase
An early trace-buffer allocation failure can leave tracing state uninitialized and cause a later tracefs worker to crash the kernel during boot.
6. Manual review advice
NO MANUAL CHECK NEEDED
The patch and stack trace establish only a highly constrained early-boot NULL dereference with no attacker-accessible corruption or authorization primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: tracing: Do not initialize tracefs work if tracing is disabled
Commit: e8665e884e076d894f3eed8b9ea28e37a6448604
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8665e884e076d894f3eed8b9ea28e37a6448604
Commit description:
If trace buffer allocation fails during early boot (e.g. in
early_trace_init() -> allocate_trace_buffers()), tracing_disabled is
left set to 1 and the global trace array events list remains
uninitialized.
Later during boot, tracer_init_tracefs() (invoked via fs_initcall)
queues tracerfs_init_work asynchronously without checking if tracing was
disabled. When tracer_init_tracefs_work_func() runs, it calls
event_trace_init() and init_tracer_tracefs(&global_trace, NULL)
unconditionally. This leads to __find_event_file() dereferencing an
uninitialized tr->events list, causing an early boot NULL pointer
dereference Oops:
BUG: Kernel NULL pointer dereference on read at 0x00000010
Faulting instruction address: 0xc000000000485be0
Oops: Kernel access of bad area, sig: 7 [#1]
...
NIP [c000000000485be0] __find_event_file+0x70/0x3c0
LR [c000000000448874] init_tracer_tracefs+0x274/0xc80
Call Trace:
init_tracer_tracefs+0x274/0xc80
tracer_init_tracefs_work_func+0x50/0x320
process_one_work+0x1e8/0x5c0
worker_thread+0x1dc/0x3d0
kthread+0x194/0x1b0
start_kernel_thread+0x14/0x18
Check tracing_disabled at the beginning of tracer_init_tracefs_work_func()
and return immediately if tracing is disabled or failed to initialize,
preventing the crash.
Cc: [email protected]
Fixes: 6621a70 ("tracing: make tracer_init_tracefs initcall asynchronous")
Link: https://patch.msgid.link/[email protected]
Reported-by: Michal Suchánek <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Amit Machhiwal <[email protected]>
Tested-by: Michal Suchánek <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
kernel/trace/trace.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=e8665e884e076d894f3eed8b9ea28e37a6448604
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99247 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99247
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: Not available
The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.1
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: 0
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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).
reply other threads:[~2026-11-04 2:45 UTC|newest]
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