[CVE-2026-64299][MODERATE REGULAR] tracing: Prevent out-of-bounds read in glob matching

[CVE-2026-64299][MODERATE REGULAR] tracing: Prevent out-of-bounds read in glob matching

[AL-KERNEL]

CVE: CVE-2026-64299
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: tracing: Prevent out-of-bounds read in glob matching
Commit: 265f3a690f6c7d69ef7d2ca50b04b4853a211df3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=265f3a690f6c7d69ef7d2ca50b04b4853a211df3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64299
Analysis date: Sat, 25 Jul 2026 08:30:36 -0400
ActionableScore: 4
ActionableScore lower bound: 1
Actionable bucket: Borderline manual review recommended
Manual review required: YES

Summary:
A length handling bug in tracing glob filters can make regex_match_glob read beyond non NUL terminated trace event string fields, causing a kernel slab out of bounds read with possible limited information disclosure or local DoS when tracing filters are accessible.

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

The original Linux kernel CVE announcement for CVE-2026-64299 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64299

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 REGULAR
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-2026-64299	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';CWE-125;CWE-126;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.1';DESCR 'A slab out of bounds read can occur in the tracing event filter path because regex_match_glob used glob_match on trace event string fields that are not always NUL terminated. A local actor able to install a glob based trace event filter can make glob matching read beyond the recorded field boundary when a matching tracepoint such as xfs_lookup is triggered. For the CVSS the PR:L is used for the paranoid score because some deployments delegate tracing or tracefs access to service accounts, containers, or non root operators even though the typical default configuration requires administrator privileges. The issue is not network reachable and is triggered through local tracing control plane configuration rather than packet or remote input. Impact is at least local denial of service on KASAN or hardened systems and may allow limited confidentiality impact through an out of bounds read side channel, but there is no supported write primitive or direct privilege escalation path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended (with actual score 3)	YES	READ KASAN OOB DISK LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Confidentiality impact plausible: +1. The bug is a concrete slab out of bounds read in kernel memory, but no direct user visible leak channel is demonstrated.
* Availability impact realistic: +1. KASAN reports slab out of bounds read, and hardened or debug kernels may turn this into a crash.
* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. Installing trace event filters through tracing or tracefs is normally restricted.

Paranoid signals:

* Local unprivileged trigger: +1. Some deployments delegate tracing or tracefs access to service accounts, containers, or non root operators.
* Reliable kernel crash / strong DoS: +1. The OOB read is reachable through a tracepoint path and can trigger KASAN or hardened kernel failures.
* Confidentiality impact plausible: +1. The matcher may read beyond the event field boundary, creating a limited OOB read primitive.
* Broad/default/common subsystem exposure: +1. Tracing and event filters are common kernel facilities, although access is usually restricted.

Not counted:

* No generic memory corruption bonus. This is read-only OOB, not UAF, OOB write, type confusion, or double free.
* No privilege escalation bonus. The patch does not show reclaim, write primitive, callback control, object replacement, or refcount abuse.
* No network reachability. Triggering is through local tracing control plane configuration.

## 3. Reachability analysis

A local actor who can install a glob based trace event filter can trigger the bug when a tracepoint with a non NUL terminated string field is evaluated, for example the mentioned xfs_lookup path. In normal production configurations this requires administrative tracing privileges, commonly root or CAP_SYS_ADMIN. In delegated tracing environments, containers, service accounts, or non root operators may have enough access, which justifies the paranoid PR:L interpretation. The path is not remotely reachable through packets or network input.

Call-site confidence: high. The commit explicitly identifies regex_match_glob, filter_match_preds, and xfs_lookup as the reachable call path.

## 4. Severity interpretation

This behaves more like a borderline actionable Moderate than an Important issue. Theoretical impact includes limited kernel memory disclosure or crash, but realistic exploitation evidence is limited to slab out of bounds read detection and no write or lifetime corruption primitive is shown. It should not be auto-closed solely as a low-risk tracing bug, because it is a concrete kernel OOB read in a common subsystem.

## 5. One-sentence report phrase

A length handling bug in tracing glob filters can make regex_match_glob read beyond non NUL terminated trace event string fields, causing a kernel slab out of bounds read with possible limited information disclosure or local DoS when tracing filters are accessible.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because this is a concrete kernel out of bounds read with possible confidentiality and crash impact, but the absence of a write primitive or LPE path keeps it below Important in the conservative assessment.

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

Patch: tracing: Prevent out-of-bounds read in glob matching
Commit: 265f3a690f6c7d69ef7d2ca50b04b4853a211df3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=265f3a690f6c7d69ef7d2ca50b04b4853a211df3

Commit description:

String event fields are not necessarily NUL-terminated, so the filter
predicate functions (filter_pred_string(), filter_pred_strloc() and
filter_pred_strrelloc()) pass the field length to the regex match
callbacks, and the length-aware matchers honour it.

regex_match_glob() was the exception: it ignored the length and called
glob_match(), which scans the string until it hits a NUL byte. Some
string fields are not NUL-terminated. One example is the dynamic char
array of the xfs_* namespace tracepoints, which is copied without a
trailing NUL. For such a field, glob matching reads past the end of
the event field, causing a KASAN slab-out-of-bounds read in
glob_match(), reached via regex_match_glob() and filter_match_preds()
from the xfs_lookup tracepoint.

Add a length-bounded glob_match_len() and use it from regex_match_glob()
so glob matching always stops at the field boundary. The matching loop
is factored into a shared helper so glob_match() keeps its behaviour.

Fixes: 60f1d5e ("ftrace: Support full glob matching")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/da1aaf125fc3b63320b0c540fd6afa7c3d5b4f1a.1782836943.git.hhhuang@smu.edu.sg
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Zhengchuan Liang <zcliangcn@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Assisted-by: Codex:GPT-5.4
Signed-off-by: Huihui Huang <hhhuang@smu.edu.sg>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  include/linux/glob.h
  kernel/trace/trace_events_filter.c
  lib/glob.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=265f3a690f6c7d69ef7d2ca50b04b4853a211df3

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

The original Linux kernel CVE announcement for CVE-2026-64299 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64299

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:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 6.1

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: 1
  Paranoid ActionableScore: 4

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).