From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99238][MODERATE 7.0] tracing: Hold trace_types_lock when updating modules in persistent instances Date: Mon, 02 Nov 2026 22:24:15 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99238 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 57408eac99b0d8a005796346d317d31f0ca4e07a List-Id: CVE: CVE-2026-99238 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: tracing: Hold trace_types_lock when updating modules in persistent instances Commit: 57408eac99b0d8a005796346d317d31f0ca4e07a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=57408eac99b0d8a005796346d317d31f0ca4e07a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99238 Analysis date: Mon, 02 Nov 2026 22:24:15 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A host-administrator-triggered race lets the module notifier traverse a concurrently removed and freed tracing instance, causing a crash-capable `trace_array` use-after-free. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99238 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99238 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-99238 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99238 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC TEMP_DISTANCE_MERGE=LOW->MODERATE;AEGIS=MODERATE_KPANIC;GAP=2 (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'A race in trace_module_record can let the module notifier walk ftrace_trace_arrays while a concurrent tracing instance rmdir removes and frees a trace_array. This creates a kernel use after free because the notifier may read flags or continue module processing through a stale trace_array pointer. For the CVSS the PR:H value is selected because reliable triggering normally requires permission to remove tracefs instances and to load or unload kernel modules. AC:H reflects the need to win a concurrency window. The demonstrated impact is a local kernel crash and denial of service. Reuse of the freed kernel object could theoretically affect confidentiality or integrity, but no controlled write or proven privilege escalation primitive is established. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 6.4 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to MODERATE_KPANIC 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 TEMP_DISTANCE_MERGE and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 1.9 and ActionableScore 0 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE TRACE LEAK UAF LINUS TEMP_DISTANCE_MERGE KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=YES NamespaceScopedPrivilege=NO 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 * Raw paranoid score: 1 * Paranoid score: 1 * No floor or cap applied; the UAF floors do not apply because host-admin-equivalent privilege is positively supported. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +2 Real UAF: `trace_module_record()` traverses `ftrace_trace_arrays` without `trace_types_lock`, while concurrent instance removal can unlink and free the same `trace_array`. * +1 Reliable kernel crash/DoS: the supplied evidence supports a stale dereference and local kernel crash. * -2 Host-admin-equivalent trigger: reliably controlling module load/unload and tracefs instance removal requires broad host capabilities, including module-management authority. * No race penalty: concurrency is required, but the evidence does not establish a sufficiently narrow, one-shot, or externally uncontrollable race. * No structured-stale leverage: the notifier reads active `trace_array` state, but attacker-controlled reclaim, replacement contents, callback control, or directed writes are not shown. * No confidentiality, integrity, extra availability, or LPE points. The same crash is counted only once. * NEW52/B5-R does not apply: no retry-accumulated heap OOB write exists. NEW53 and B4-PENDING are also inapplicable. 3. Reachability analysis The complete reliable trigger is local and host-administrative: one path removes a tracing instance while a module load or unload invokes the notifier. These operations are not shown to be available through user or trace namespaces, and no below-host-admin actor controlling the complete race is established. Numeric UID 0 is not intrinsically required because equivalent capabilities can supply the authority. No special hardware is needed. 4. Primitive and severity reading This is a real CLASS_B active-structured-object UAF, not fixed stale storage. The freed `trace_array` remains visible to a notifier traversal, which reads flags and may continue persistent-instance module processing. The demonstrated consequence is crash/DoS. There is no repeated release/refcount mutation, controlled reclaim, OOB write, disclosure, authorization bypass, or security-boundary crossing. Consequently, Important-grade leverage is unsupported and automatic Moderate downgrade remains permissible. 5. One-sentence report phrase A host-administrator-triggered race lets the module notifier traverse a concurrently removed and freed tracing instance, causing a crash-capable `trace_array` use-after-free. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm that no product-specific delegation permits a below-host-admin actor to remove instances while independently inducing module notifier activity. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: tracing: Hold trace_types_lock when updating modules in persistent instances Commit: 57408eac99b0d8a005796346d317d31f0ca4e07a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=57408eac99b0d8a005796346d317d31f0ca4e07a Commit description: trace_module_record() walks ftrace_trace_arrays from the module notifier without trace_types_lock. A concurrent rmdir of an instance removes it from the list and frees it under that lock, so a module load or unload can walk into a freed trace_array. Cc: stable@vger.kernel.org Fixes: 5f3719f ("tracing: Update modules to persistent instances when loaded") Link: https://patch.msgid.link/20261016061638.214847-1-devnexen@gmail.com Signed-off-by: David Carlier Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman 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=57408eac99b0d8a005796346d317d31f0ca4e07a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99238 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99238 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:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 6.4 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: 1 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).