From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64309][MODERATE 7.0] crypto: ccp - Do not initialize SNP for ioctl(SNP_COMMIT) Date: Sat, 25 Jul 2026 15:05:16 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64309 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 74768f73854d647a6462f252dc8782ab8a835211 List-Id: CVE: CVE-2026-64309 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: crypto: ccp - Do not initialize SNP for ioctl(SNP_COMMIT) Commit: 74768f73854d647a6462f252dc8782ab8a835211 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=74768f73854d647a6462f252dc8782ab8a835211 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64309 Analysis date: Sat, 25 Jul 2026 15:05:16 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A local process with access to the SEV device ioctl path may cause `SNP_COMMIT` to incorrectly disturb SEV/SNP firmware state, potentially leading to a later KVM `VMRUN` fault and host-wide denial of service on affected AMD virtualization hosts. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64309 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64309 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-2026-64309 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-665;CWE-703;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'SNP_COMMIT could incorrectly force SEV-SNP initialization and shutdown even though the firmware command is allowed when SNP was previously uninitialized. On an AMD SEV or SEV-SNP capable virtualization host this can disturb global firmware or SVM state while normal KVM VMs are running, and a later VMRUN may hit a general protection fault and crash the host. For the CVSS the PR:L value is used because reliable triggering requires local access to /dev/sev or an equivalent delegated virtualization management context, but not necessarily full host root in practical deployments. The issue is not network reachable by itself and must be triggered through a local ioctl path. Impact is denial of service for the host and running VMs. No UAF, OOB access, information leak, or arbitrary write primitive is visible from the provided patch context, so confidentiality and integrity are not raised.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES DANGER INIT SIMPLEFIX DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: **3** * Paranoid score: **5** * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * **Firmware-mediated external influence: +1**. The vulnerable path interacts with AMD SEV/SNP firmware state through `SEV_CMD_SNP_COMMIT`. * **Privileged kernel/device-management state path: +1**. The bug affects SEV/SNP platform state used by KVM/SVM, not just local driver bookkeeping. * **Reliable kernel crash / strong DoS: +1**. The described failure mode can lead to a host crash when a later `VMRUN` hits a general protection fault. * **Availability impact realistic: +1**. The impact can affect the host and active VMs, not only the calling process. * **Practical chain strongly implied: +1**. The report describes a concrete local ioctl path leading to global SEV/SVM state disruption and later host failure. * **Special platform and state preconditions: -1**. Requires AMD SEV/SNP-capable hardware and relevant firmware/KVM state. * **Restricted local device access: -1**. Triggering requires access to `/dev/sev` or an equivalent virtualization-management context. Paranoid interpretation removes the two negative adjustments because on affected virtualization hosts `/dev/sev` access may be delegated to non-root service accounts and active KVM workloads are expected. This yields **5**. Not awarded: * No generic memory corruption bonus. The patch does not show UAF, OOB access, double free, type confusion, arbitrary write, or refcount abuse. * No confidentiality or integrity impact. The visible primitive is host/VM availability loss. * No remote/network trigger. The path is a local ioctl path. ## 3. Reachability analysis The bug is locally triggerable by a process that can issue SEV/SNP ioctls through `/dev/sev` or an equivalent device node exposed to a virtualization management component. It is not network reachable by itself. In typical deployments, direct access to `/dev/sev` is restricted, but this should not automatically be treated as full host-root only. Some virtualization stacks may delegate this access to QEMU, libvirt, or other service accounts with reduced privileges. Containers or namespaces do not normally make `/dev/sev` available unless explicitly passed through, but if delegated, the attacker may not need full host-root capabilities. The issue is configuration and hardware dependent. It matters mainly on AMD SEV or SEV-SNP capable KVM hosts where active VMs are running. ## 4. Severity interpretation This behaves more like an **Actionable Moderate** than an ordinary Low/Moderate cleanup because it can disrupt global virtualization state and crash the host, affecting active guest workloads. It does **not** currently look like an Important memory-corruption vulnerability. The patch removes unnecessary SNP initialization and shutdown around `SNP_COMMIT`; it does not expose a concrete UAF, OOB write, stale callback, arbitrary write, or privilege-escalation primitive. The paranoid score is justified for triage because the affected path is a virtualization host control path and the failure can be host-wide. It should not be auto-closed without checking real `/dev/sev` permissions and affected product configuration. ## 5. One-sentence report phrase A local process with access to the SEV device ioctl path may cause `SNP_COMMIT` to incorrectly disturb SEV/SNP firmware state, potentially leading to a later KVM `VMRUN` fault and host-wide denial of service on affected AMD virtualization hosts. ## 6. Manual review recommendation **MANUAL CHECK REQUIRED** Manual review is required to confirm `/dev/sev` permissions, whether access is delegated to non-root virtualization services, affected AMD SEV/SNP platform behavior, and whether active KVM workloads can be crashed reliably. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: crypto: ccp - Do not initialize SNP for ioctl(SNP_COMMIT) Commit: 74768f73854d647a6462f252dc8782ab8a835211 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=74768f73854d647a6462f252dc8782ab8a835211 Commit description: Sashiko notes: > if SEV initialization fails and KVM is actively running normal VMs, could a > userspace process trigger this code path via /dev/sev ioctls (e.g., > SEV_PDH_GEN) and zero out MSR_VM_HSAVE_PA globally? Would the next VMRUN > execution for an active VM trigger a general protection fault and crash the > host? The SNP_COMMIT command does not require the firmware to be in any particular state. Skip initializing it if it was previously uninitialized. The SEV-SNP firmware specification doc 56860 does not mention SNP_COMMIT in Table 5 as a command that is allowed in the UNINIT state, but it is in fact allowed and a future documentation update will reflect that. Fixes: ceac7fb ("crypto: ccp - Ensure implicit SEV/SNP init and shutdown in ioctls") Reported-by: Sashiko Assisted-by: Gemini:gemini-3.1-pro-preview Link: https://sashiko.dev/#/patchset/20260324161301.1353976-1-tycho%40kernel.org CC: Signed-off-by: Tycho Andersen (AMD) Reviewed-by: Tom Lendacky Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman Changed files: drivers/crypto/ccp/sev-dev.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=74768f73854d647a6462f252dc8782ab8a835211 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64309 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64309 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:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: 3 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: NO 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).