From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-43206][IMPORTANT] drm/amdkfd: Fix out-of-bounds write in kfd_event_page_set() [ Upstream Date: Thu, 30 Jul 2026 12:50:12 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-43206 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: 8 X-AL-KERNEL-ActionableScore-Lower: 7 X-AL-KERNEL-Commit: 3e04bc310d80b46eaf481f1fefcbcb37a187412d List-Id: CVE: CVE-2026-43206 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: drm/amdkfd: Fix out-of-bounds write in kfd_event_page_set() [ Upstream Commit: 3e04bc310d80b46eaf481f1fefcbcb37a187412d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3e04bc310d80b46eaf481f1fefcbcb37a187412d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43206 Analysis date: Thu, 30 Jul 2026 12:50:12 -0400 ActionableScore: 8 ActionableScore lower bound: 7 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: An unprivileged local user with access to the AMD KFD device can provide an undersized event page buffer and trigger an out-of-bounds kernel memset in kfd_event_page_set(), causing kernel memory corruption with possible privilege escalation or denial of service. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43206 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43206 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-2026-43206 IMPORTANT CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-119;*CWE-20;BEST CVSS score: '7.8';DESCR 'An out-of-bounds write in the AMD KFD event page setup path occurs because kfd_event_page_set() writes KFD_SIGNAL_EVENT_LIMIT * 8 bytes without first validating that the supplied event page buffer is large enough. A local userspace process with access to the KFD device can pass a too small buffer and cause kernel memory corruption. For the CVSS the PR:L is used because exploitation requires local code execution and access to the GPU KFD interface, but it does not require full administrator privileges. The issue is not network reachable. Impact can include kernel crash and potential privilege escalation because the primitive is an out-of-bounds kernel write rather than a DoS-only failure.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) MAYBE WRITE OOB SIMPLEFIX HARDWARE KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=7 ## 1. ActionableScore * Conservative score: 7 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown * Local unprivileged trigger: +1 The commit explicitly says unprivileged userspace can pass a small buffer and trigger the bug. * Memory corruption, strong corruption primitive: +2 The bug is an out-of-bounds kernel memory write caused by memset() writing KFD_SIGNAL_EVENT_LIMIT * 8 bytes without validating the supplied size. * Strong LPE plausibility: +2 The primitive is a kernel OOB write from a local userspace reachable GPU/KFD path, and the commit explicitly mentions potential privilege escalation. * Reliable kernel crash / strong DoS: +1 Even if privilege escalation is not reliable, an OOB kernel write is sufficient for a realistic local kernel crash. * Integrity impact plausible: +1 Kernel memory can be overwritten beyond the intended event page buffer. Even if the memset payload is fixed, this is still a plausible kernel data integrity violation. * Availability impact realistic: +1 for paranoid score only The trigger appears simple and local, so a host-wide crash is plausible. This is counted only in the paranoid score to avoid excessive double-counting with the DoS signal. Not counted: * Remote reachable: +0 This is not network-triggerable. * High-control GPU API bonus: +0 The affected path is a GPU/KFD userspace interface, but the patch only shows size misuse. It does not show allocator shaping, callback control, refcount control, DMA ownership control, or object lifetime control beyond the OOB write itself. * Confidentiality impact: +0 The patch shows an OOB write, not a read-back or information disclosure primitive. ## 3. Reachability analysis A local userspace process with access to the AMD KFD interface can trigger the bug by supplying an event page buffer smaller than KFD_SIGNAL_EVENT_LIMIT * 8. In typical deployments this likely requires access to /dev/kfd or the relevant DRM/KFD device node, but not full administrator privileges. Container impact depends on whether GPU device nodes are passed into the container. If /dev/kfd is exposed to an untrusted container or service account, the practical PR remains low. The path is not remotely reachable and depends on systems using AMDGPU/KFD functionality. Call-site confidence: medium. The patch shows the vulnerable validation point and the commit explicitly describes the OOB write and unprivileged trigger, but the full ioctl call chain is not included in the provided input. ## 4. Severity interpretation This behaves like an Important-class local kernel memory corruption issue, not an ordinary Moderate DoS. The realistic impact includes local kernel crash, and the patch context supports potential privilege escalation because the primitive is an out-of-bounds kernel write. Theoretical exploitability may depend on what object lies after the undersized event page buffer and how controllable the surrounding layout is, but the bug class and unprivileged reachability make auto-closure inappropriate. ## 5. One-sentence report phrase An unprivileged local user with access to the AMD KFD device can provide an undersized event page buffer and trigger an out-of-bounds kernel memset in kfd_event_page_set(), causing kernel memory corruption with possible privilege escalation or denial of service. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the issue is an explicitly described unprivileged out-of-bounds kernel memory write with potential privilege escalation, so it should be reviewed manually even if the exact overwrite target and exploit reliability require further analysis. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdkfd: Fix out-of-bounds write in kfd_event_page_set() [ Upstream Commit: 3e04bc310d80b46eaf481f1fefcbcb37a187412d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3e04bc310d80b46eaf481f1fefcbcb37a187412d Changed files: drivers/gpu/drm/amd/amdkfd/kfd_events.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=3e04bc310d80b46eaf481f1fefcbcb37a187412d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43206 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43206 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:L/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.8 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: 7 Paranoid ActionableScore: 8 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).