[CVE-2026-99219][LOW] ftrace: Initialize modname and offset in print_rec()

[CVE-2026-99219][LOW] ftrace: Initialize modname and offset in print_rec()

[AL-KERNEL]

CVE: CVE-2026-99219
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ftrace: Initialize modname and offset in print_rec()
Commit: 753d5cba113a52cb155428f4ea93a4b0148c4bf1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=753d5cba113a52cb155428f4ea93a4b0148c4bf1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99219
Analysis date: Mon, 02 Nov 2026 22:18:00 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A timed tracefs read can pass an uninitialized module-name pointer to `seq_printf()`, causing a kernel Oops and possibly an unconfirmed limited disclosure.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-99219 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99219

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-2026-99219	LOW	https://www.kernelcve.org/list/?q=CVE-2026-99219 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: LOW, Aegis: 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:L/I:N/A:H';CWE-824;*CWE-457;CWE-362;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'An uninitialized pointer dereference in ftrace print_rec occurs when kallsyms_lookup fails during module loading or unloading and leaves modname and offset unchanged. A concurrent read of available_filter_functions can pass a garbage modname value through the pointer check and seq_printf can treat it as a string pointer, causing a kernel Oops and potentially a system panic. If the garbage pointer references mapped memory, limited kernel data disclosure through the tracefs output is plausible but not demonstrated or controllable. For the CVSS the PR:L value reflects a local process that can read the relevant tracefs file. AC:H reflects the required timing with module loading or unloading. The issue is not directly network reachable and no write primitive or supported privilege escalation path is present. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to LOW because the cross model evidence reconciliation rule was applied. 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. Exact triggered rule markers were V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS unavailable and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	MAYBE	TRACE LEAK LINUS  V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED	-	-	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 2.
* Paranoid score: 2; no floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Reliable kernel crash/strong DoS: failed `kallsyms_lookup()` leaves `modname` uninitialized; a garbage non-NULL pointer reaches `seq_printf()` and the supplied trace confirms an Oops.
* +1 Local unprivileged trigger: supplied evidence grounds reading `available_filter_functions` from a local low-privilege process.
* -1 Hard timing requirement: lookup failure requires the read to coincide with module loading or unloading, which the reader is not shown to control.
* Paranoid +1 Confidentiality plausible: if the garbage pointer happens to reference mapped memory, `%s` may return bytes through the seq-file read rather than faulting. This is a concrete output path, but no successful disclosure or pointer control is demonstrated.
* No UAF, OOB write, shared-backing write, authorization bypass, controlled target, or privilege-escalation primitive is shown.
* No extra availability point is awarded for the same Oops. NEW52 B5-R and NEW53 B3-PENDING do not apply.

3. Reachability analysis

A below-host-admin local reader can exercise the vulnerable tracefs read, so host UID 0 is not required for that operation. However, successful triggering depends on a concurrent module lifecycle event; the attacker is not shown able to initiate it. Namespace capability scope is not established. No remote path, special hardware, or attacker-controlled retry sequence exists.

4. Primitive and severity reading

The primitive is an uninitialized stack pointer consumed as a string pointer. It is neither active structured-state corruption nor a lifetime violation. The demonstrated result is an invalid dereference and kernel Oops, hence CLASS_C. Limited disclosure is technically possible through `seq_printf()` but remains unconfirmed and uncontrollable. There is no Important-preserving corrupt or trust-boundary chain, so automatic Moderate downgrade remains permissible.

5. One-sentence report phrase

A timed tracefs read can pass an uninitialized module-name pointer to `seq_printf()`, causing a kernel Oops and possibly an unconfirmed limited disclosure.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm tracefs permissions, panic-on-oops policy, and whether any successful mapped-pointer disclosure is reproducible.

7. Call-site confidence

Call-site confidence: high

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

Patch: ftrace: Initialize modname and offset in print_rec()
Commit: 753d5cba113a52cb155428f4ea93a4b0148c4bf1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=753d5cba113a52cb155428f4ea93a4b0148c4bf1

Commit description:

print_rec() leaves 'modname' and 'offset' uninitialized and
kallsyms_lookup() only sets them on success. When the lookup fails like
when a module is being loaded or unloaded, 'modname' holds a garbage
value, passes the 'if (modname)' check, and is dereferenced by
seq_printf().

  Oops: general protection fault
  RIP: 0010:string+0x48/0xe0
  Call Trace:
   vsnprintf+0x1f5/0x650
   seq_printf+0x8e/0xb0
   print_rec+0x6c/0xc0
   t_show+0x4c/0x440
   seq_read_iter+0x119/0x480

This can be triggered by reading available_filter_functions while a
module is being loaded or unloaded.

Initialize both variables so a failed lookup skips the module name.

Cc: stable@vger.kernel.org
Fixes: b39181f ("ftrace: Add FTRACE_MCOUNT_MAX_OFFSET to avoid adding weak function")
Link: https://patch.msgid.link/20261016230403.4916-1-aarnahmd@amazon.com
Tested-by: Gavin Inglis <giinglis@amazon.com>
Signed-off-by: Aaron Ahmed <aarnahmd@amazon.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  kernel/trace/ftrace.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=753d5cba113a52cb155428f4ea93a4b0148c4bf1

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

The original Linux kernel CVE announcement for CVE-2026-99219 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99219

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:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/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: 1
  Paranoid ActionableScore: 2

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