From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90220][MODERATE REGULAR] ALSA: seq: Don't leak the extension cell pointer in the bounce payload [ Upstream Date: Thu, 17 Sep 2026 23:12:56 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90220 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: 42c3f856d13a91a0d4c302a0c6854813621136db List-Id: CVE: CVE-2026-90220 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ALSA: seq: Don't leak the extension cell pointer in the bounce payload [ Upstream Commit: 42c3f856d13a91a0d4c302a0c6854813621136db Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=42c3f856d13a91a0d4c302a0c6854813621136db Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90220 Analysis date: Thu, 17 Sep 2026 23:12:56 -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-2026-90220 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90220 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-2026-90220 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90220 CHECK WITH IMPACT FROM ORIG NN MODERATE 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:N/A:N';*CWE-200;CWE-201;CWE-497;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.5';DESCR 'An information disclosure in the ALSA sequencer bounce path can expose a kernel heap pointer because bounce_error_event embeds a queued variable length event without clearing its data.ext.ptr field. An unprivileged local client can enable SNDRV_SEQ_FILTER_BOUNCE, queue a variable length event to a nonexistent port, and read the returned bounce payload containing an eight byte kernel address on a 64 bit system. For the CVSS the PR:L value is used because triggering requires a local unprivileged process with access to the ALSA sequencer interface. The issue is not network reachable and does not require user interaction. The direct impact is disclosure of a kernel heap address, which may weaken address randomization and assist exploitation of a separate memory corruption flaw. No direct write, kernel crash, or privilege escalation primitive is present in this bug alone.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) SKIP CVE-2026-90220 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE READ OOB LEAK HARDWARE LINUS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 PrimitiveClass=NONE RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO 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 signals: * +1 Local unprivileged trigger. The commit explicitly establishes that an unprivileged ALSA sequencer client can request bounce events and receive the leaked pointer. * +1 Confidentiality plausible. A concrete eight-byte kernel heap address is copied to userspace on 64-bit systems. * Total: 2. Additional paranoid signal: * +1 Weak exploitation concern. The disclosed extension-cell address can reduce kernel heap address uncertainty and may assist exploitation of a separate memory-corruption flaw. * Total: 3. Not awarded: * No UAF, OOB write, arbitrary write, controlled reclaim, or object corruption is established. * No integrity, availability, or privilege-escalation consequence is demonstrated. * No practical LPE chain is established. * No remote reachability exists. * No broad-exposure point is awarded because ALSA may be common, but this specific sequencer bounce path is not shown to be routinely exercised. * No strong exploitation-leverage points are awarded because the disclosure is one pointer from the clients own event pool rather than a substantial memory disclosure. 3. Reachability analysis An ordinary local user with access to the ALSA sequencer interface can enable `SNDRV_SEQ_FILTER_BOUNCE`, queue a variable-length event to a nonexistent port, and read the resulting bounce event. No host-admin capability, namespace-scoped capability, prior privileged setup, special hardware, race, or timing window is required. The path is local only. It is not reachable through network traffic. Availability may depend on ALSA sequencer support and device-node access, but the commit positively identifies an unprivileged client as the complete attacker. 4. Primitive and severity interpretation The exact primitive is a direct disclosure of one kernel heap pointer stored in `data.ext.ptr`. The pointer reaches userspace because the embedded variable-length event is copied verbatim into the bounce payload. This is not a stale-object use, UAF, active-object corruption, or repeated lifetime mutation. `RealUAF=NO`. No write or crash primitive exists. `PrimitiveClass=NONE` is used because the leak is limited and does not satisfy Class A substantial-disclosure criteria, while Classes B and C describe corruption, lifetime, or crash-oriented primitives not present here. The demonstrated consequence is an eight-byte kernel address disclosure. The defensible worst case is weakening KASLR or heap-layout uncertainty for use with another vulnerability. This does not independently establish privilege escalation. `ImportantCandidate=NO` because no Important-grade corruption or boundary-bypass primitive is present. `AutoDowngradeAllowed=YES` because the issue is a bounded local pointer disclosure without an unresolved corruption primitive. Manual review remains recommended to determine the practical stability and KASLR value of the leaked extension-cell address. 5. One-sentence report phrase An unprivileged local ALSA sequencer client can receive an unsanitized extension-cell pointer in a bounce payload, disclosing a kernel heap address that may weaken address randomization but does not independently provide memory corruption or privilege escalation. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Confirm whether the leaked extension-cell address is stable enough to provide a practical KASLR or heap-layout bypass, but the supplied evidence does not support Important-class severity. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: seq: Don't leak the extension cell pointer in the bounce payload [ Upstream Commit: 42c3f856d13a91a0d4c302a0c6854813621136db Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=42c3f856d13a91a0d4c302a0c6854813621136db Changed files: sound/core/seq/seq_clientmgr.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=42c3f856d13a91a0d4c302a0c6854813621136db ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90220 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90220 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:L/UI:N/S:U/C:L/I:N/A:N The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N The Best / paranoid CVSS score: 5.5 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).