From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98086][MODERATE REGULAR] ALSA: ump: do not touch legacy_rmidi before it exists [ Upstream Date: Fri, 25 Sep 2026 13:47:57 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98086 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: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: 1c8e01792adf91879322f1ad752f1814de8b7e7d List-Id: CVE: CVE-2026-98086 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ALSA: ump: do not touch legacy_rmidi before it exists [ Upstream Commit: 1c8e01792adf91879322f1ad752f1814de8b7e7d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1c8e01792adf91879322f1ad752f1814de8b7e7d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98086 Analysis date: Fri, 25 Sep 2026 13:47:57 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98086 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98086 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98086 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98086 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-362;CWE-665;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.6';DESCR 'An ALSA UMP endpoint message can reach the legacy rawmidi naming helpers after endpoint parsing has been marked complete but before legacy_rmidi has been created and attached. If a UMP packet arrives through snd_ump_receive during this initialization window, ump_legacy_set_rawmidi_name can pass a field derived from a NULL rawmidi pointer to snprintf and trigger a kernel fault in IRQ context. For the CVSS the PR:N value is used because an attacker controlling an attached UMP endpoint does not need a local account or privileges on the target system. The issue is not network reachable through the ordinary network stack and normally requires control of a physically connected or otherwise hardware backed MIDI UMP endpoint. Impact is denial of service through a kernel Oops or panic. The shown code provides no UAF, information leak, OOB access, or write primitive into valid kernel memory that would support privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE KASAN NULLPTR SIMPLEFIX HARDWARE LINUS PACKET INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 2 * Paranoid score: 2 * No floor or cap was applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Conservative signals: * +1 Firmware or device mediated external influence. A UMP endpoint controls the packet delivered through `snd_ump_receive()`. * +1 Reliable kernel crash or strong DoS. `snprintf()` receives a destination derived from a NULL `legacy_rmidi` pointer in IRQ context, with a KASAN NULL-pointer dereference already observed. * -1 Narrow hardware timing. The packet must arrive during the initialization window after `parsed` is set but before `legacy_rmidi` is attached. Paranoid adjustment: * The -1 timing penalty is withheld because a deliberately programmed endpoint may be able to send packets promptly and repeatedly during device initialization. Not awarded: * No UAF exists. The rawmidi object has not yet been created or attached rather than having been freed. * No valid-memory overwrite, controlled target, controlled reclaim, OOB access, disclosure, repeated release, or refcount mutation is established. * No C or I impact and no privilege-escalation leverage are demonstrated. * No remote-network bonus applies. * No additional Availability point is awarded because it would double-count the same crash. * No physical or rare-hardware penalty is applied because the supplied evidence does not prove that every affected UMP transport requires uncommon hardware. 3. Reachability analysis The supported attacker model is a malicious or malfunctioning UMP endpoint capable of delivering an endpoint-name packet during device initialization. Such an endpoint does not require a host account or host-administrator privilege, so `HostAdminRequired=NO`. Ordinary local-user software injection is not established. The path is not directly network reachable, and no namespace capability participates in the trigger. Device attachment and driver probing can occur automatically, but control of a suitable endpoint is required. The conservative analysis treats the initialization window as narrow. The paranoid analysis recognizes that endpoint firmware may influence packet timing across repeated enumeration attempts. 4. Primitive and severity interpretation The exact primitive is a NULL-derived destination passed to `snprintf()`, producing an invalid low-address write attempt and immediate kernel fault. This is an initialization-order logic race and Class C crash behavior, not stale storage, UAF, or active-object lifetime corruption. There is no first lifetime-ending operation, surviving dangling reference, or second release/refcount mutation. The demonstrated consequence is kernel Oops or panic. Privilege escalation and useful memory corruption remain unsupported theoretical outcomes. `ImportantCandidate=NO` because no independently useful corruption, ownership, authorization, or lifetime primitive survives after excluding the crash. `AutoDowngradeAllowed=YES` because the issue is a constrained NULL dereference with no unresolved Class A or Class B leverage. 5. One-sentence report phrase A malicious or malfunctioning ALSA UMP endpoint can deliver a packet before legacy rawmidi initialization completes and trigger a NULL-pointer dereference in IRQ context, causing a host kernel denial of service. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Confirm which UMP transport drivers can deliver packets during this window and whether any software-only, remotely mediated, or ordinary local-user injection path exists. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: ump: do not touch legacy_rmidi before it exists [ Upstream Commit: 1c8e01792adf91879322f1ad752f1814de8b7e7d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1c8e01792adf91879322f1ad752f1814de8b7e7d Changed files: sound/core/ump.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=1c8e01792adf91879322f1ad752f1814de8b7e7d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98086 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98086 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:N/I:N/A:H The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.6 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: 1 Paranoid ActionableScore: 2 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).