From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90289][MODERATE REGULAR] drm/amd/display: Resize MST HDCP per-connector arrays to 32 [ Upstream Date: Thu, 17 Sep 2026 14:47:40 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90289 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 0fa116a17b69a28712cdf209318e345b676d7f6c List-Id: CVE: CVE-2026-90289 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/amd/display: Resize MST HDCP per-connector arrays to 32 [ Upstream Commit: 0fa116a17b69a28712cdf209318e345b676d7f6c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0fa116a17b69a28712cdf209318e345b676d7f6c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90289 Analysis date: Thu, 17 Sep 2026 14:47:40 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90289 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90289 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 REGULAR 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-2026-90289 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90289 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:H/I:H/A:H';CWE-193;*CWE-787;CWE-125;CWE-129;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'The MST HDCP state uses several per connector arrays that were allocated for only 31 entries even though DRM can expose 32 connectors. Access for the last connector can use index 31 and may read or write beyond the affected arrays into adjacent fields of struct hdcp_workqueue. The most concerning case is an out of bounds pointer write after the aconnector array, which can corrupt nearby mutex or HDCP state and cause a kernel crash. A controlled privilege escalation primitive is not demonstrated, but memory corruption means confidentiality and integrity impact cannot be excluded without reviewing all index assignment paths. For the CVSS the PR:L value is used for the paranoid score because a local process may be able to trigger DRM or MST connector reprobe and HDCP state handling when a 32 connector topology is present. Attack complexity is high because the issue depends on an uncommon maximum size MST topology and specific connector lifecycle operations. The issue is not network reachable and normally requires local or physical access to the display topology. Impact is at least denial of service and in the worst defensible case may include confidentiality, integrity, or privilege escalation impact due to an out of bounds kernel memory access.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) SKIP CVE-2026-90289 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE DANGER SIMPLEFIX HARDWARE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 PrimitiveClass=CLASS_B RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2 * Raw paranoid score: 3 * Paranoid score: 3 * No floor or cap was applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Conservative positive signals: * +1 Constrained kernel buffer overwrite. Arrays intended for 32 connectors had only 31 elements. An index of 31 can produce a bounded one-past write, but the target is fixed adjacent storage and the written values appear to be kernel-derived connector or HDCP state rather than an attacker-selected payload. * +1 Weak or indirect corruption candidate. An out-of-bounds access to `aconnector[31]` can overlap the following `mutex` storage. A corresponding read could reinterpret adjacent bytes as a connector pointer, while a write could damage synchronization state. Paranoid additional signal: * +1 Realistic kernel crash. Corruption of a mutex or later use of an invalid connector pointer can plausibly cause an Oops, lock corruption, or kernel failure. This is not counted again as a separate availability impact. No negative points: * No host-admin penalty was applied because the complete privilege boundary is unresolved. * No physical or rare-hardware penalty was applied. AMDGPU is not inherently rare, and the supplied evidence does not prove that 32 simultaneously attached physical displays are required rather than connector creation or MST lifecycle churn reaching index 31. * No race penalty was applied because this is an array-size mismatch, not a timing race. Important non-awarded signals: * Strong corruption leverage was not awarded. The destination is a fixed one-past location, and arbitrary target or payload selection is not demonstrated. * Controlled reclaim, arbitrary kernel read or write, callback control, credential corruption, and privilege escalation are not established. * Confidentiality was not awarded because no disclosure path is shown. * Integrity impact beyond corruption of local HDCP or synchronization state is not established. * Local unprivileged reachability was not awarded because the complete DRM master, compositor, KMS, MST, and HDCP trigger path is not supplied. * Remote reachability is not established. * Memory-layout-invariant restoration was not scored separately because it would duplicate the bounds mismatch. * No UAF or repeated lifetime/refcount operation exists. 3. Reachability analysis The affected path requires AMDGPU display management with DisplayPort MST and HDCP state handling. Reaching the problematic final array element requires connector index 31, but the supplied context does not show whether this requires 32 concurrent connectors or can result from repeated MST connector creation and removal. An ordinary logged-in user does not automatically control KMS or MST topology. A DRM master, compositor, display server, or delegated graphics service may be able to initiate connector probing and HDCP property processing, but the supplied call paths do not establish that such an actor can complete the trigger below host-admin privilege. Therefore `HostAdminRequired=UNKNOWN`. No namespace-scoped capability path is shown. DRM display hardware and MST topology are not made namespace-reachable merely by creating a user or network namespace, so `NamespaceScopedPrivilege=UNKNOWN`. Prior setup includes a compatible AMD GPU and an MST/HDCP configuration capable of reaching the final connector slot. There is no timing race. Once index 31 is reached, the bounds mismatch is deterministic, although the exact vulnerable reader or writer is absent from the supplied diff. 4. Primitive and severity interpretation The exact candidate primitive is a bounded one-past access to per-connector arrays embedded in `struct hdcp_workqueue`. The most security-relevant array is `aconnector`, because its one-past element overlaps the following mutex according to the visible structure layout. Other arrays can overwrite neighboring HDCP state or the trailing `max_link` field. This is active structured-object corruption rather than fixed stale storage. It is not a UAF, cleanup double release, refcount error, or ownership violation. The patch establishes an allocation/count mismatch but does not include the direct index-assignment call sites. Consequently, there is medium confidence that connector index 31 reaches an actual out-of-bounds reader or writer, but insufficient evidence for attacker-directed corruption. `PrimitiveClass=CLASS_B` reflects a real kernel object-corruption candidate requiring call-site analysis. It is not Class A because controlled payload, controlled destination, arbitrary access, or meaningful security-boundary bypass is not demonstrated. The practical consequence supported by normal structure semantics is corruption of HDCP or mutex state with a plausible crash. Privilege escalation remains theoretical and is not scored. `ImportantCandidate=NO` because the established primitive is bounded and constrained, without demonstrated exploitation leverage beyond crash. `AutoDowngradeAllowed=YES` because no controlled corruption or unresolved Important-grade primitive is currently established, though review is recommended before closure. Likely operational severity is ordinary to borderline Moderate and highly dependent on whether an accessible call site can assign connector index 31. 5. One-sentence report phrase The AMDGPU MST HDCP code allocated per-connector arrays for 31 entries despite supporting 32 connectors, creating a bounded one-past kernel object access that can corrupt adjacent HDCP or mutex state and plausibly cause a kernel crash. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Inspect all readers and writers of `aconnector`, `encryption_status`, `content_protection`, and `hdcp_content_type` to confirm whether index 31 is reachable, what values are written, and whether a below-host-admin DRM actor can drive the complete MST and HDCP sequence. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amd/display: Resize MST HDCP per-connector arrays to 32 [ Upstream Commit: 0fa116a17b69a28712cdf209318e345b676d7f6c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0fa116a17b69a28712cdf209318e345b676d7f6c Changed files: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_hdcp.c drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_hdcp.h 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=0fa116a17b69a28712cdf209318e345b676d7f6c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90289 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90289 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:P/AC:H/PR:N/UI:N/S:U/C:L/I:L/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: 2 Paranoid ActionableScore: 3 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 REGULAR 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).