[CVE-2026-97934][MODERATE 7.0] tracing: Fix memory corruption from a "STACKTRACE" histogram key

[CVE-2026-97934][MODERATE 7.0] tracing: Fix memory corruption from a "STACKTRACE" histogram key

[AL-KERNEL]

CVE: CVE-2026-97934
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: tracing: Fix memory corruption from a "STACKTRACE" histogram key
Commit: 9e026a91fe79966e2baabd4345c6e3a26975c729
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9e026a91fe79966e2baabd4345c6e3a26975c729
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97934
Analysis date: Fri, 25 Sep 2026 16:40:12 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-97934 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97934

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-2026-97934	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-97934 CHECK WITH IMPACT FROM ORIG NN LOW	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-20;CWE-119;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 memory corruption flaw in the tracing histogram path occurs because the generic STACKTRACE field is returned as a non NULL placeholder and is then treated as a real stacktrace field. The histogram code reads an expected __data_loc value from offset 0, interprets data derived from common_type as a record offset, and uses a value found there as the length of an unbounded memcpy. A local actor with access to tracefs histogram triggers can select a suitable event and generate a record that reaches the invalid copy, causing a general protection fault and kernel panic. For the CVSS the PR:L value is used for the paranoid score because tracing access may be delegated to a reduced capability administrator, container root, or diagnostic service even when full host root access is unavailable. The demonstrated impact is local denial of service. The explicit unbounded memcpy also creates a credible memory corruption primitive that may permit confidentiality or integrity impact and potential privilege escalation, so manual review is required. The issue is not directly network reachable.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)  SKIP CVE-2026-97934 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	READ OOB TRACE HARDWARE LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	-	-	checked

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

ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 5
* Raw paranoid score: 4
* Paranoid score: 5
* Conservative adjustment: 3 -> 5 under the manual-review safety floor for a concrete Class A semantic reinterpretation and kernel overwrite primitive.
* Paranoid adjustment: 4 -> 5 under the same floor.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2 Strong attacker-influenced semantic reinterpretation and corruption primitive. The generic STACKTRACE placeholder is treated as a real dynamic stacktrace field. Data beginning at common_type is reinterpreted as __data_loc metadata, producing a bogus offset and an unbounded memcpy length.
* +1 Reliable kernel crash. The supplied reproducer reaches memcpy and causes a general protection fault followed by kernel panic.
* Total: 3.

Paranoid additional signal:

* +1 Active memory-access consequence of semantic reinterpretation. The incorrectly interpreted values directly control the offset and length consumed by memcpy. This is stronger than passive metadata corruption, although it does not establish an arbitrary write.
* Total: 4.

Material signals not awarded:

* No UAF or post-lifetime object use is established.
* Controlled reclaim, arbitrary write, directed target selection, callback control, and privilege escalation are not demonstrated.
* No confidentiality or separate integrity consequence is awarded merely because the copy corrupts memory.
* No additional Availability point is awarded because it would duplicate the demonstrated kernel panic.
* Local unprivileged reachability is not established.
* Host-admin penalty is not applied because mandatory host-admin-equivalent privilege is not positively established.
* Remote reachability is not established.
* No race or timing penalty applies. The supplied trigger is an ordered and apparently deterministic sequence.
* No repeated release, refcount mutation, or lifetime floor applies.

3. Reachability analysis

The trigger requires writing a histogram definition containing STACKTRACE to an event trigger file and then generating the selected trace event through trace_marker. These tracefs operations are normally permission-gated, and the reproducer uses a privileged shell prompt, but the supplied evidence does not prove that host-admin-equivalent privilege is mandatory in every configuration. Trace instances and files can be delegated to tracing or diagnostic services, so HostAdminRequired remains UNKNOWN rather than YES.

Tracefs access is not made namespace-scoped merely by acquiring capabilities in an attacker-created user namespace. No complete namespace-local trigger chain is shown, so NamespaceScopedPrivilege is NO. Prior administrative setup may be required to mount or delegate tracefs, but that prerequisite is not resolved by the supplied patch. No special hardware, networking exposure, boot mode, or race timing is required.

4. Primitive and severity interpretation

The exact primitive is attacker-selected semantic misclassification of a generic histogram field. A placeholder with offset and size zero survives parse_field(), causing create_hist_field() to select stacktrace handling. The record header is then interpreted as dynamic-location metadata, and data reached through the resulting offset supplies an unbounded memcpy length.

This is neither a UAF nor fixed stale storage. It is an active parsing and memory-copy path with a concrete kernel overwrite or over-copy condition. The demonstrated consequence is host kernel panic. The patch supports meaningful corruption beyond a simple invalid pointer dereference, but it does not establish arbitrary target selection, controlled payload placement, information disclosure, or privilege escalation.

PrimitiveClass is CLASS_A because the semantic reinterpretation directly controls active memory-access parameters and reaches an unbounded kernel memcpy. ImportantCandidate is YES because exploitation leverage beyond the demonstrated crash remains unresolved. AutoDowngradeAllowed is NO because automatically treating the issue as ordinary DoS would discard a concrete Class A corruption primitive. Operationally, it is Actionable Moderate at minimum and requires review to determine whether the destination layout and event selection permit useful non-crash corruption.

5. One-sentence report phrase

A malformed tracing histogram STACKTRACE key causes record header data to be reinterpreted as dynamic stacktrace metadata, resulting in an unbounded kernel memcpy and a reproducible kernel panic with unresolved non-crash corruption potential.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Review the memcpy destination size, event-dependent offset selection, controllability of the copied bytes and length, adjacent histogram object layout, and real tracefs delegation model to determine whether the primitive can be converted from panic into controlled kernel corruption.

7. Call-site confidence

Call-site confidence: medium

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

Patch: tracing: Fix memory corruption from a "STACKTRACE" histogram key
Commit: 9e026a91fe79966e2baabd4345c6e3a26975c729
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9e026a91fe79966e2baabd4345c6e3a26975c729

Commit description:

"cpu", "CPU", "stacktrace" and "STACKTRACE" are generic fields, defined
with an offset and a size of zero so that the filter code can match them
by name. parse_field() maps them onto their common_* equivalents for
backward compatibility, but unlike the common_* names it hands the
placeholder back to the caller instead of NULL.

create_hist_field() takes a non-NULL field as a promise that the record
carries a stacktrace and picks HIST_FIELD_FN_STACK, so the __data_loc
word is read from offset 0, that is from common_type, and its low 16
bits are followed as an offset into the record. What is found there
becomes the length of an unbounded memcpy. Pick an event whose id is
small enough that the offset stays inside its own record and the length
is a kernel text address:

  # cd /sys/kernel/tracing
  # echo 'hist:keys=STACKTRACE' > events/ftrace/print/trigger
  # echo hello > trace_marker

  Oops: general protection fault, probably for non-canonical address
  RIP: 0010:rb_next+0x23/0x60
   </IRQ>
  RIP: 0010:memcpy+0xc/0x30
   event_hist_trigger+0x2e7/0x12c0
  Kernel panic - not syncing: Fatal exception in interrupt

Leave the field NULL, which is what the comment above the branch says
the code does and what common_stacktrace already does. FILTER_CPU and
FILTER_COMM are left alone, their create_hist_field() branches never
look at the field.

Cc: stable@vger.kernel.org
Fixes: 4b51286 ("tracing: Rename stacktrace field to common_stacktrace")
Link: https://patch.msgid.link/20260907155045.692664-3-donggeunyoo.kernel@gmail.com
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  kernel/trace/trace_events_hist.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=9e026a91fe79966e2baabd4345c6e3a26975c729

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

The original Linux kernel CVE announcement for CVE-2026-97934 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97934

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