From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72289][IMPORTANT] KVM: arm64: vgic: Check the interrupt is still ours before migrating it Date: Sat, 15 Aug 2026 22:51:17 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72289 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 7 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 3893e1fcf6f306b327a8358dcd1cbd077989a240 List-Id: CVE: CVE-2026-72289 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: KVM: arm64: vgic: Check the interrupt is still ours before migrating it Commit: 3893e1fcf6f306b327a8358dcd1cbd077989a240 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3893e1fcf6f306b327a8358dcd1cbd077989a240 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72289 Analysis date: Sat, 15 Aug 2026 22:51:17 -0400 ActionableScore: 7 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A race in KVM arm64 VGIC interrupt migration can double delete an interrupt from a vCPU pending list after it was concurrently removed, allowing a local guest or KVM user to trigger host kernel list corruption and at least a denial of service. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72289 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72289 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: IMPORTANT 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-2026-72289 IMPORTANT CHECK WITH IMPACT FROM ORIG NN LOW 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-362;*CWE-787;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'KVM arm64 vgic has a race in vgic_prune_ap_list while migrating a pending interrupt between vCPUs. The code drops locks and later checks only that the target affinity is unchanged, but the interrupt may already have been removed from the old ap_list by vgic_flush_pending_lpis while enabled and pending state still makes the affinity check pass. This can make list_del run a second time on an already removed list entry, leading to host kernel list corruption or a crash. For the CVSS the PR:L is used because the attacker typically needs the ability to run or control a guest VM or local KVM context, not full host administrator privileges. The issue is not directly network reachable and is a local or guest-to-host virtualization attack surface. Impact is at least denial of service on the host. For the paranoid score, choose the highest still defensible interpretation supported by the bug class and patch context, with preference for manual-review sensitivity over autoclosed false negatives.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6) YES VIRT INIT SIMPLEFIX DMAorINTERRUPT HARDWARE LINUS KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 7 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. Triggering appears possible from a local KVM guest or local user able to run/control a VM, typically not requiring full host root. * Memory corruption, weak/indirect corruption candidate: +1. The bug can cause a second `list_del()` on an already removed VGIC interrupt list entry. * Reliable kernel crash / strong DoS: +1. Kernel list corruption or invalid list manipulation can realistically crash the host. * Broad/default/common subsystem exposure: +1. KVM is a common virtualization attack surface on arm64 systems where guests are supported. * Hard or unreliable race / special timing required: -1. The bug requires a race between VGIC interrupt migration and pending LPI flushing. * Privileged kernel/device-management memory corruption path: +1. The corruption occurs inside KVM VGIC interrupt management, a trusted host kernel virtualization path. Paranoid additional interpretation: * Memory corruption, strong corruption primitive: +2 instead of weak +1. A double `list_del()` can corrupt kernel list pointers, not merely cause a NULL dereference. * Weak LPE concern: +1. Guest-to-host list corruption in KVM is a manual-review class even without a demonstrated reclaim or arbitrary write primitive. * Real lifetime/ownership corruption: +1. The interrupt is no longer owned by the old vCPU list, but stale assumptions allow the old path to operate on it again. ## 3. Reachability analysis The realistic trigger requires local KVM access or the ability to control a guest VM on an affected arm64 host. This is PR:L in practical terms, because `/dev/kvm` access is commonly delegated to non-root users or VM-management services, although exact reachability depends on host policy. It is not directly network reachable. A remote attacker would need an additional path to control a guest workload or VM-management interface. Namespaces do not automatically make this reachable, but reduced-privilege service accounts, containerized VM managers, or users in the `kvm` group may have enough access. The race is timing dependent, so exploitation is not trivial, but the affected path is a real KVM host attack surface. ## 4. Severity interpretation This is more than an ordinary Moderate because the failure mode is not just validation failure or a WARN. The patch prevents a stale ownership assumption that can make `list_del()` run twice on the same list node. Realistically demonstrated impact is host DoS through list corruption or crash. Theoretical privilege escalation is not proven, because the patch does not show attacker-controlled reclaim, arbitrary write, callback control, or controlled object replacement. However, because this is KVM guest-to-host reachable list corruption in host kernel interrupt state, the paranoid score should remain high enough for manual review. ## 5. One-sentence report phrase A race in KVM arm64 VGIC interrupt migration can double delete an interrupt from a vCPU pending list after it was concurrently removed, allowing a local guest or KVM user to trigger host kernel list corruption and at least a denial of service. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a KVM guest-to-host attack surface with a race-dependent double `list_del()` and possible host kernel list corruption. Even though practical LPE is not demonstrated, this class should not be auto-closed. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: KVM: arm64: vgic: Check the interrupt is still ours before migrating it Commit: 3893e1fcf6f306b327a8358dcd1cbd077989a240 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3893e1fcf6f306b327a8358dcd1cbd077989a240 Commit description: vgic_prune_ap_list() drops both ap_list_lock and irq_lock while migrating an interrupt to another vCPU. After reacquiring the locks it only checks that the affinity is unchanged (target_vcpu == vgic_target_oracle(irq)) before moving the interrupt, which assumes that an interrupt whose affinity is preserved is still queued on this vCPU's ap_list. That assumption no longer holds if the interrupt is taken off the ap_list while the locks are dropped. vgic_flush_pending_lpis() removes the interrupt from the list and sets irq->vcpu to NULL, but leaves enabled/pending/target_vcpu untouched. As the interrupt is still enabled and pending, vgic_target_oracle() returns the same target_vcpu, so the affinity check passes and list_del() is run a second time on an entry that has already been removed. Also check that the interrupt is still assigned to this vCPU (irq->vcpu == vcpu) before moving it. Fixes: 0919e84 ("KVM: arm/arm64: vgic-new: Add IRQ sync/flush framework") Signed-off-by: Hyunwoo Kim Link: https://patch.msgid.link/aiHnI1mu6SGQrgnz@v4bel Signed-off-by: Marc Zyngier Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: arch/arm64/kvm/vgic/vgic.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=3893e1fcf6f306b327a8358dcd1cbd077989a240 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72289 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72289 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:L/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: 7 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).