From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-97997][LOW] virtio_ring: fix stale descriptor flags after a failed packed add [ Upstream Date: Fri, 25 Sep 2026 13:46:38 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-97997 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: d595358276b60e5df4d3930bc94033249b1d5adc List-Id: CVE: CVE-2026-97997 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: virtio_ring: fix stale descriptor flags after a failed packed add [ Upstream Commit: d595358276b60e5df4d3930bc94033249b1d5adc Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d595358276b60e5df4d3930bc94033249b1d5adc Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97997 Analysis date: Fri, 25 Sep 2026 13:46:38 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97997 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97997 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: LOW 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-2026-97997 LOW https://www.kernelcve.org/list/?q=CVE-2026-97997 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-665;**CWE-400;CWE-703;BEST CVSS score: '4.7';DESCR 'A failed mapping of a packed virtqueue request can leave AVAIL and USED flags in descriptors that were already prepared before the failure. A later shorter request at the same ring position can cause the virtio device to interpret stale descriptors as part of that request, blocking the queue and preventing further I O completion. For the CVSS the PR:L because a local process must generate I O activity to reach the affected driver path. Exploitation also requires packed virtqueues and typically swiotlb memory pressure that causes a partial mapping failure. The issue is not directly network reachable. Impact is denial of service for the affected virtio queue or guest workload. No memory corruption primitive is demonstrated by the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES VIRT HARDWARE LINUS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 1 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Concrete queue availability failure. The patch establishes that stale AVAIL and USED descriptor flags can cause a later shorter request to be interpreted as extending into stale descriptors, blocking the affected packed virtqueue. * No UAF signal. The patch does not show an object being freed and subsequently accessed. * No arbitrary or directed write. The changed writes only invalidate stale descriptor flags in the driver owned virtqueue ring. * No controlled reclaim, callback dispatch, refcount corruption, disclosure, integrity violation, or privilege escalation primitive is demonstrated. * No remote reachability signal. Triggering requires local I O activity through an already configured virtio device. * No local unprivileged trigger signal awarded. A local workload may contribute to the failure, but the complete required environment includes packed virtqueue support, a swiotlb related mapping failure, and memory pressure. The supplied evidence does not establish that an ordinary unprivileged user can reliably arrange the complete sequence in the evaluated deployment. * No hard race penalty. This is an ordered rollback and stale ring state issue, not a timing race. * No niche subsystem penalty. Packed virtqueues and swiotlb conditions are relevant exposure constraints, but the evidence does not establish that they are impossible or exceptionally inaccessible. 3. Reachability analysis The affected path is reached when the Linux virtio driver submits a packed virtqueue request and vring_map_one_sg fails after some non head descriptors have already been marked available. A later request must reuse the same ring position and be shorter than the aborted request. The commit identifies swiotlb configurations under memory pressure and larger I O requests as the typical condition for partial mapping failure. This is not directly network reachable. It is also not a guest to host escape primitive based on the supplied material. The demonstrated impact is within the system using the affected virtqueue, such as a guest workload or the affected virtio device queue. HostAdminRequired is UNKNOWN. The patch does not prove that host administrator privileges are required to generate relevant I O, but it also does not prove that an ordinary local user can reliably cause the required packed ring and swiotlb mapping failure sequence. NamespaceScopedPrivilege is UNKNOWN because no namespace specific capability or complete namespace scoped trigger chain is shown. 4. Primitive and severity interpretation The primitive is a stale packed virtqueue descriptor state. After a partial mapping failure, non head descriptors retain AVAIL and USED bits even though the request was aborted and its mappings were released. A later shorter request can therefore be semantically extended by stale descriptors, causing the device to stop making progress and block the queue. This is invalid active ring state and queue availability failure, not a real use after free, double release, refcount mutation, out of bounds access, or controlled memory corruption primitive. The stale descriptors are driver generated ring entries. The patch and commit explicitly describe queue blocking and restored request completion after invalidating those entries. They do not establish device DMA into arbitrary stale mappings, host memory corruption, confidentiality impact, integrity impact, guest to host impact, or privilege escalation. PrimitiveClass is CLASS_C because the established behavior is a constrained invalid state resulting in device or workload denial of service. ImportantCandidate is NO because meaningful exploitation leverage beyond queue blocking is not established. AutoDowngradeAllowed is YES because no unresolved concrete corruption, ownership, lifetime, or security boundary primitive remains. 5. One-sentence report phrase A failed packed virtqueue mapping can leave stale descriptor availability flags that cause a later shorter request to consume invalid descriptors and block the affected virtio queue. 6. Manual review recommendation NO MANUAL CHECK NEEDED The supplied patch establishes a queue blocking denial of service condition only. It does not establish memory corruption, a lifetime violation, a security boundary bypass, remote reachability, or privilege escalation. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: virtio_ring: fix stale descriptor flags after a failed packed add [ Upstream Commit: d595358276b60e5df4d3930bc94033249b1d5adc Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d595358276b60e5df4d3930bc94033249b1d5adc Changed files: drivers/virtio/virtio_ring.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=d595358276b60e5df4d3930bc94033249b1d5adc ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97997 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97997 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: Not available The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).