From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98968][MODERATE 7.0] amt: send the relay's General Query directly from the receive path [ Upstream Date: Mon, 26 Oct 2026 23:28:46 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98968 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: 95114e421196250e3d9662f12df442799477d3c3 List-Id: CVE: CVE-2026-98968 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: amt: send the relay's General Query directly from the receive path [ Upstream Commit: 95114e421196250e3d9662f12df442799477d3c3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95114e421196250e3d9662f12df442799477d3c3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98968 Analysis date: Mon, 26 Oct 2026 23:28:46 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: A remotely induced AMT tunnel can expire while a delayed query skb retains its raw pointer, causing later host transmit processing to dereference freed structured tunnel state. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98968 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98968 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-2026-98968 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98968 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-825;*CWE-664;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'An AMT relay General Query could remain queued in a qdisc after the referenced tunnel was removed because the skb cb area stored a raw tunnel pointer lacking lifetime protection. A later dequeue enters amt_dev_xmit and dereferences the freed amt_tunnel_list object in amt_send_membership_query, producing a confirmed slab use after free and allowing a kernel crash. Reliable exploitation requires the query skb to remain queued beyond the tunnel lifetime, such as the demonstrated 180 second netem delay against a 135 second tunnel lifetime, so AC:H is appropriate. For the CVSS the PR:N value is selected because after a vulnerable delayed qdisc is present a remote AMT participant can initiate the relevant tunnel and query processing lacking a local user context. The base impact is availability loss. The paranoid score allows limited confidentiality and integrity impact because reclaimed tunnel memory may be consumed through the stale pointer, but no arbitrary write or reliable privilege escalation primitive is established. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because FD false positive review allowed a downgrade. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH. The independent weaker Aegis shadow evaluated CVSS 4.1 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE UAF NETWORK SKB HARDWARE QDISC IPV6 KPANIC PACKET KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=NO NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 4. * Conservative score: 4; no floor or cap changed it. * Raw paranoid score: 5. * Paranoid score: 5; no floor or cap changed it. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown * +2 Real UAF: `skb->cb` retains a raw `amt_tunnel_list` pointer after tunnel expiry; delayed dequeue dereferences it in `amt_dev_xmit()`/`amt_send_membership_query()`. * +1 Reliable kernel crash/DoS: KASAN confirms slab use-after-free in the transmit path; a fatal kernel fault is plausible. * +1 Attacker-influenced lifetime sequence: after delayed-qdisc setup, a remote AMT participant can induce tunnel/query processing, and deterministic tunnel expiry precedes dequeue. * Paranoid +1 structured stale-object leverage: the stale active tunnel object is passed into membership-query processing rather than merely checked or immediately discarded. Exact consumed fields and useful reuse behavior are not supplied, so this is omitted from the conservative score. * No -1 race penalty: the demonstrated 180-second queue delay versus 135-second lifetime is an ordered delay/expiry sequence, not a narrow uncontrollable race. * Remote-reachability +2 withheld because vulnerable timing depends on prior privileged delayed-qdisc configuration. * Controlled reclaim, attacker-shaped replacement contents, arbitrary write, disclosure, LPE, and separate C/I impact are not shown. * No extra availability point; it would duplicate the same crash. * No repeated release/refcount mutation exists. 3. Reachability analysis A remote AMT participant can trigger the relevant processing without host-admin powers once a sufficiently delayed qdisc is installed. Installing netem is separate privileged setup; the supplied evidence does not resolve whether that setup can be wholly namespace-scoped. No special hardware is required. The long delay raises operational complexity but is repeatable and deterministic. 4. Primitive and severity reading This is an active structured-object UAF, not fixed stale storage: a queued skb outlives and later supplies a freed tunnel pointer to privileged host networking code. The shown effect is host-kernel UAF/crash. Useful post-reuse processing remains unresolved, and no Class A exploit primitive is proven. The credible remote-participant-to-host-relay boundary, attacker-influenced lifetime sequence, and later host-kernel consumption make this a V33 Class B Important review candidate. Auto-downgrade is unsafe despite the absence of proven arbitrary write or LPE. 5. One-sentence report phrase A remotely induced AMT tunnel can expire while a delayed query skb retains its raw pointer, causing later host transmit processing to dereference freed structured tunnel state. 6. Manual review advice MANUAL CHECK REQUIRED Review exact tunnel fields consumed after dequeue, reclaim opportunities, and deployment exposure of delayed qdiscs. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: amt: send the relay's General Query directly from the receive path [ Upstream Commit: 95114e421196250e3d9662f12df442799477d3c3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95114e421196250e3d9662f12df442799477d3c3 Changed files: drivers/net/amt.c include/net/amt.h 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=95114e421196250e3d9662f12df442799477d3c3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98968 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98968 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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/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).