From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64520][MODERATE 7.0] firmware: arm_ffa: Bound PARTITION_INFO_GET_REGS copies [ Upstream Date: Sat, 25 Jul 2026 08:09:08 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64520 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: 7 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: f39bc7ebe75e2186b417a024a7f7e2fd4cc7eb95 List-Id: CVE: CVE-2026-64520 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: firmware: arm_ffa: Bound PARTITION_INFO_GET_REGS copies [ Upstream Commit: f39bc7ebe75e2186b417a024a7f7e2fd4cc7eb95 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f39bc7ebe75e2186b417a024a7f7e2fd4cc7eb95 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64520 Analysis date: Sat, 25 Jul 2026 08:09:08 -0400 ActionableScore: 7 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: The register based FF-A PARTITION_INFO_GET path trusted firmware supplied indices while copying descriptors into a kernel array, allowing a malicious or inconsistent FF-A provider to trigger an out of bounds write and potential kernel memory corruption. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64520 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64520 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-2026-64520 MODERATE 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-787;*CWE-20;CWE-129;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H';BEST CVSS score: '7';DESCR 'The register based FFA_PARTITION_INFO_GET path trusted firmware supplied descriptor counts and current indices while copying partition descriptors into a caller provided kernel array. A malicious or inconsistent FF-A provider could make the copy loop advance beyond the allocated array and corrupt adjacent kernel memory. For the CVSS the PR:L is used for the paranoid score because some deployments may expose the returned partition information through a less privileged secure partition, TEE service, or delegated management path rather than only fully trusted platform firmware. The issue is local to the ARM FF-A firmware interface and is not directly network reachable. Impact can include kernel memory corruption, denial of service, and in the worst case confidentiality and integrity impact if the overwrite is controllable enough for further exploitation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6) SKIP CVE-2026-64520 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE LINUS KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS - - 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: * Firmware-mediated external influence: +1. The corrupting indices and descriptor counts come from FF-A firmware or an FF-A provider. * Constrained kernel buffer overwrite: +1. The copy can advance past the caller allocated `struct ffa_partition_info` array, but the target is adjacent memory rather than an attacker chosen address. * Privileged kernel/device-management memory corruption path: +1. The overwrite happens inside a trusted firmware interface path. * Integrity impact plausible: +1. Writing past a kernel array can corrupt adjacent kernel state. * No attacker-controlled target selection: -1. The overwrite location is constrained by the layout of the allocated caller buffer. Paranoid additional interpretation: * Memory corruption, strong corruption primitive: +2 instead of constrained +1. The patch explicitly prevents writes past the allocated array. * Weak LPE concern: +1. If a less privileged secure partition, TEE service, or delegated firmware-management path can influence FF-A responses, this becomes a cross-boundary kernel memory corruption concern. * Confidentiality impact plausible: +1. Kernel memory corruption may affect objects that later expose data, although no direct info leak is shown. * Availability impact realistic: +1. Adjacent kernel memory corruption can plausibly crash the kernel. * Integrity impact plausible: +1. The overwrite can modify kernel memory. No remote reachable bonus is applied. This is not a normal network-triggerable path. ## 3. Reachability analysis The direct input source is firmware or an FF-A provider returning inconsistent `count`, `cur_idx`, or fragmented descriptor progress values. A normal local unprivileged Linux user typically cannot control this interface directly, so the conservative view treats this as firmware-mediated and not ordinary local-user reachable. Namespaces and containers do not meaningfully lower the privilege requirement unless the deployment exposes FF-A partition discovery through a delegated TEE or management service reachable by less privileged code. The affected path is platform-specific to ARM FF-A systems and is not a broad default exposure on all Linux systems. Realistic exploitation requires either faulty firmware, malicious firmware, a compromised secure partition, or a platform design where a less trusted component can influence the returned partition information. ## 4. Severity interpretation This is not an ordinary Moderate bookkeeping issue because the patch fixes a concrete out-of-bounds write into a kernel caller buffer. The realistic exploitation evidence is limited by the firmware-mediated reachability and constrained overwrite target, so the conservative score remains borderline. The paranoid score is higher because the bug class is kernel memory corruption and the trust boundary can be meaningful on systems where secure partitions or TEE services are less trusted than the normal-world kernel. This should be handled as at least Actionable Moderate, with Important-candidate treatment for affected ARM FF-A deployments. ## 5. One-sentence report phrase The register based FF-A PARTITION_INFO_GET path trusted firmware supplied indices while copying descriptors into a kernel array, allowing a malicious or inconsistent FF-A provider to trigger an out of bounds write and potential kernel memory corruption. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch fixes an explicit out-of-bounds write in a trusted firmware interface path, and the practical severity depends on platform-specific FF-A trust boundaries and whether less privileged secure components can influence the returned descriptors. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: firmware: arm_ffa: Bound PARTITION_INFO_GET_REGS copies [ Upstream Commit: f39bc7ebe75e2186b417a024a7f7e2fd4cc7eb95 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f39bc7ebe75e2186b417a024a7f7e2fd4cc7eb95 Changed files: drivers/firmware/arm_ffa/driver.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=f39bc7ebe75e2186b417a024a7f7e2fd4cc7eb95 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64520 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64520 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:L/PR:H/UI:N/S:U/C:H/I:H/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: 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).