From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90002][MODERATE 7.0] ftrace: Take trace_array reference before accessing its ftrace_ops [ Upstream Date: Wed, 16 Sep 2026 15:06:48 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90002 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 83fd7eca5ab0d3ac3f23bff889175d847e21af06 List-Id: CVE: CVE-2026-90002 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: ftrace: Take trace_array reference before accessing its ftrace_ops [ Upstream Commit: 83fd7eca5ab0d3ac3f23bff889175d847e21af06 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83fd7eca5ab0d3ac3f23bff889175d847e21af06 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90002 Analysis date: Wed, 16 Sep 2026 15:06:48 -0400 ActionableScore: 5 ActionableScore lower bound: 4 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-2026-90002 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90002 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-2026-90002 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90002 CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in ftrace trace instance handling can cause a use-after-free when set_ftrace_filter or set_ftrace_notrace is opened while the same trace instance is being removed. The old open path could read ftrace_ops from inode private data before safely taking a trace_array reference, so a concurrent rmdir could free the ftrace_ops and leave the opener dereferencing stale kernel memory. For the CVSS the PR:L is used for the paranoid score because local code execution with delegated tracefs access or reduced administrative tracing access may be enough to race file open against trace instance removal. The issue is not network reachable and requires local interaction with tracefs control files. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel use-after-free, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) YES INIT TRACE NOMEMCHK RACE UAF KERNEL_PANIC_PLUS_UAF LINUS KPANIC KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 3 * Conservative score: 4 * Raw paranoid score: 4 * Paranoid score: 5 * Applied conservative floor/cap: Real UAF floor 4 applied, 3 -> 4 * Applied paranoid floor/cap: Real UAF floor 5 applied, 4 -> 5 * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown Conservative signals: * +2 Real UAF / lifetime violation. The commit directly states that ftrace_ops can be freed by concurrent rmdir while set_ftrace_filter or set_ftrace_notrace open still dereferences it. * +1 Reliable kernel crash / strong DoS. The supplied text says the UAF can crash the kernel. * +1 Attacker influenced lifetime sequence. The same actor with trace instance control can race opening the filter file against removing the trace instance. * -1 Hard timing. The commit describes a small race window where rmdir must overlap file open. * No -2 host admin penalty. Host admin equivalent access is likely in default tracefs deployments, but the supplied evidence does not positively prove that no delegated tracing access model can reach the complete operation. Paranoid signals: * +2 Real UAF / lifetime violation. Same as conservative. * +1 Reliable kernel crash / strong DoS. Same as conservative. * +1 Attacker influenced lifetime sequence. Same as conservative. * +1 Structured stale object concern. ftrace_ops is an active structured kernel object and the stale path consumes it to obtain trace_array state and enter ftrace filter open handling. * -1 Hard timing. Same as conservative. Important non-awarded signals: * Controlled reclaim is not demonstrated. * Arbitrary kernel read or write is not demonstrated. * Function pointer or callback hijack is not demonstrated. * Concrete repeated release/refcount mutation is not established. * Weak LPE is not separately awarded. * Extra Availability is not awarded because the same kernel crash is already counted. * C/I are not awarded as separate ActionableScore signals because confidentiality or integrity impact beyond UAF uncertainty is not concretely established. * Remote reachability is not established. * Namespace scoped privilege is not established. Repeated release/refcount checklist: * First release can end lifetime: not the scored mechanism here. * Exact same reference survives to a second lifetime mutation: not established. * Second operation is a real lifetime/refcount mutation: not established. * +1 Concrete repeated release/refcount: not awarded. * Paranoid repeated-refcount leverage +1: not awarded. * FLOOR 5: applied for paranoid because this is an active structured UAF in ftrace control path with unresolved exploitation leverage, not because of a double release. 3. Reachability analysis The trigger requires local interaction with tracefs instance files. The vulnerable sequence is opening set_ftrace_filter or set_ftrace_notrace while the same trace instance is removed with rmdir. Default tracefs control is normally restricted to root or tracing administrators, but the prompt evidence does not fully prove host-admin-equivalent privilege for all deployments. Therefore HostAdminRequired is UNKNOWN rather than YES. It is not treated as ordinary unprivileged reachability either. NamespaceScopedPrivilege is NO because tracefs tracing instance management is not shown to be fully namespace-scoped. The presence of local filesystem operations does not imply user namespace reachability. There is no network trigger. There is no special hardware prerequisite. The race is narrow because open must overlap trace instance removal, but it is repeatable if the attacker has the required tracefs control. 4. Primitive and severity interpretation The exact primitive is a use-after-free of ftrace_ops caused by taking the trace_array reference only after reading ftrace_ops from inode private data. A concurrent rmdir of the trace instance can free the ftrace_ops before the opener safely pins the owning trace_array. This is an active structured object UAF, not fixed stale storage. The demonstrated consequence is a kernel crash. The speculative consequence is broader memory corruption or privilege impact if the freed ftrace_ops storage is reused in a useful way, but controlled reclaim or arbitrary R/W is not established by the patch. PrimitiveClass is CLASS_B because a real kernel lifetime primitive exists and exploitation leverage is unresolved. It is not CLASS_A because there is no demonstrated controlled reclaim, arbitrary write, callback control, or LPE. ImportantCandidate is YES because this is a real active-object kernel UAF in ftrace control handling and should not be automatically downgraded solely to crash-only without manual review. AutoDowngradeAllowed is NO because unresolved lifetime-corruption leverage remains. Likely operational severity is Actionable Moderate with possible Important consideration after manual review, especially in products that delegate tracefs access below full host administration. 5. One-sentence report phrase A race in ftrace trace instance handling can let set_ftrace_filter or set_ftrace_notrace dereference freed ftrace_ops during concurrent instance removal, causing a local kernel UAF and at least a DoS with unresolved exploitation leverage. 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: real active-object UAF is established, the demonstrated impact is kernel crash, and exploitation leverage beyond crash is not resolved by the patch. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ftrace: Take trace_array reference before accessing its ftrace_ops [ Upstream Commit: 83fd7eca5ab0d3ac3f23bff889175d847e21af06 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83fd7eca5ab0d3ac3f23bff889175d847e21af06 Changed files: include/linux/ftrace.h kernel/trace/ftrace.c kernel/trace/trace.h kernel/trace/trace_functions.c kernel/trace/trace_stack.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=83fd7eca5ab0d3ac3f23bff889175d847e21af06 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90002 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90002 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:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7 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: 4 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).