From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64152][LOW] iommu: Handle unmap error when iommu_debug is enabled [ Upstream Date: Sun, 19 Jul 2026 15:57:55 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64152 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: 0 X-AL-KERNEL-Commit: 0cd028806efc148a75d4acf711d21db335a89661 List-Id: CVE: CVE-2026-64152 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: iommu: Handle unmap error when iommu_debug is enabled [ Upstream Commit: 0cd028806efc148a75d4acf711d21db335a89661 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0cd028806efc148a75d4acf711d21db335a89661 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64152 Analysis date: Sun, 19 Jul 2026 15:57:55 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: An IOMMU map error path could perform debug unmap tracking without a matching debug map record after partial mapping failure, causing debug-state malfunction or possible DoS only when IOMMU debug tracking is enabled. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64152 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64152 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-2026-64152 LOW 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:N/I:N/A:H';CWE-703;CWE-754;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'An error path in iommu_map_nosync can call iommu_unmap after a partial IOMMU mapping failure while iommu_debug tracking has not recorded the matching map operation. With IOMMU_DEBUG_PAGEALLOC or similar debug tracking enabled, this can create unmatched map/unmap state and may lead to warnings, debug malfunction, or denial of service in the mapping error path. For the CVSS the PR:L is used for the paranoid view because some deployments may delegate device or VFIO access to a local user or service account, allowing indirect access to IOMMU mapping paths. Reliable triggering is still high complexity because it depends on a partial map failure and a debug configuration. The issue is not network reachable and does not show a concrete information leak, UAF, OOB access, or arbitrary write primitive. Impact is best treated as availability only.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) SKIP CVE-2026-64152 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: ccc21213f013834b484cdcc738e282f963fcfc97 YES NO NO unknown MAYBE LOCK ERRORPATH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Triggered signals: * Availability impact realistic: +1 The bug can create unbalanced `iommu_debug` map/unmap tracking on a partial map failure path. The practical impact is warnings, debug-tracking malfunction, or possible DoS in debug configurations. Paranoid-only signal: * Local delegated device path concern: +1 In some deployments, VFIO or similar device access may be delegated to a local user or service account, allowing indirect interaction with IOMMU mapping paths. Subtracted signals: * Requires admin/root/device-management privileges in typical deployments: -2 Normal triggering usually requires privileged kernel/device/IOMMU mapping operations, not a general unprivileged syscall path. * Hard or unreliable trigger condition: -1 The issue requires a partial IOMMU map failure in the error path. * Non-default/debug configuration: -1 The problematic tracking path depends on `IOMMU_DEBUG_PAGEALLOC` or similar debug tracking being enabled. Not applied: * No generic memory corruption signal. The patch does not show UAF, double free, OOB write, arbitrary write, type confusion, or stale object reuse. * No privilege escalation signal. There is no supported LPE primitive. * No confidentiality or integrity signal. The bug is about unmatched debug tracking around map/unmap rollback, not disclosure or data modification. ## 3. Reachability analysis Typical reachability is local and privileged through kernel IOMMU mapping paths used by drivers, DMA, VFIO, or device-management code. It is not network reachable. Namespaces or containers do not normally expose this path unless a device or VFIO-style interface is explicitly delegated. Even then, reliable triggering requires both debug tracking enabled and a partial map failure, so exploitation conditions are narrow. Call-site confidence: high. The provided patch includes the relevant caller path in `iommu_map_nosync()` and the changed rollback behavior. ## 4. Severity interpretation This behaves like a low-end Moderate or Low-like reliability bug, not an Important-class vulnerability. The theoretical worst case is availability impact from malformed debug accounting during rollback. Realistic exploitation evidence is weak because the issue is debug-config dependent, error-path dependent, and lacks a concrete memory-corruption or privilege-escalation primitive. ## 5. One-sentence report phrase An IOMMU map error path could perform debug unmap tracking without a matching debug map record after partial mapping failure, causing debug-state malfunction or possible DoS only when IOMMU debug tracking is enabled. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed for security triage unless the evaluated product enables IOMMU debug tracking in production and delegates VFIO or device access to untrusted local users. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: iommu: Handle unmap error when iommu_debug is enabled [ Upstream Commit: 0cd028806efc148a75d4acf711d21db335a89661 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0cd028806efc148a75d4acf711d21db335a89661 Changed files: drivers/iommu/iommu.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=0cd028806efc148a75d4acf711d21db335a89661 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64152 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64152 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:H/UI:N/S:U/C:N/I:N/A:L 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: 0 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).