From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74339][MODERATE REGULAR] ALSA: seq: Clear variable event pointer on read [ Upstream Date: Sat, 15 Aug 2026 05:46:27 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74339 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: 14fe4f75fd5309d6b75f8e840ada88912b374207 List-Id: CVE: CVE-2026-74339 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ALSA: seq: Clear variable event pointer on read [ Upstream Commit: 14fe4f75fd5309d6b75f8e840ada88912b374207 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=14fe4f75fd5309d6b75f8e840ada88912b374207 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74339 Analysis date: Sat, 15 Aug 2026 05:46:27 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: A local ALSA sequencer client can read back an internal kernel pointer from a variable length event header, causing kernel address disclosure that may help bypass KASLR but does not directly provide memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74339 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74339 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-2026-74339 MODERATE 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:L/I:N/A:N';*CWE-200;CWE-497;CWE-665;BEST CVSS score: '3.3';DESCR 'ALSA sequencer snd_seq_read() can copy a variable length event header to userspace while leaving data.ext.ptr set to an internal extension cell kernel address. A local userspace sequencer client can send a direct variable event to itself and read the returned header to disclose this kernel pointer. For the CVSS the PR:L because reliable triggering requires a local user or process with access to the ALSA sequencer interface. The issue is not network reachable. Impact is information disclosure only, mainly a kernel address leak that may help bypass KASLR for another vulnerability, but this patch does not show memory corruption, arbitrary write, or direct privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3) YES OOB DANGER SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline, manual review recommended** ## 2. Signal breakdown * Local unprivileged trigger: +1 A local userspace ALSA sequencer client can send a direct variable event to itself and read the returned event header. * Confidentiality impact plausible: +1 The bug leaks an internal kernel pointer from `data.ext.ptr`, which is useful for KASLR bypass or exploit preparation. * Broad/default/common subsystem or broadly deployed exposure: +1 in paranoid score only ALSA is commonly present on desktop and multimedia systems, and `/dev/snd/seq` may be reachable by local users, but this is not universal on servers. * No generic memory corruption: +0 The patch only clears a pointer before `copy_to_user()`. It does not show UAF, OOB write, double free, type confusion, or arbitrary write. * No privilege escalation plausible from this bug alone: +0 The primitive is kernel pointer disclosure only. * No reliable kernel crash / strong DoS: +0 No crash path is described. ## 3. Reachability analysis A local user or process with access to the ALSA sequencer interface can trigger the issue. This is not remotely reachable. Namespace or container impact depends on whether the container has access to ALSA device nodes, especially `/dev/snd/seq`. The path is common on desktop systems but less consistently exposed on servers or minimal containers. Call-site confidence: high, because the relevant `copy_to_user()` path and the fixed pointer field are directly shown in the patch. ## 4. Severity interpretation This behaves like an information disclosure issue, not memory corruption. Realistic standalone impact is limited to leaking a kernel address, mainly reducing KASLR effectiveness for a separate vulnerability. It is not an Important-class issue by itself, but it is worth manual review because kernel pointer leaks can materially improve exploit reliability when chained with another kernel bug. ## 5. One-sentence report phrase A local ALSA sequencer client can read back an internal kernel pointer from a variable length event header, causing kernel address disclosure that may help bypass KASLR but does not directly provide memory corruption or privilege escalation. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED The standalone score is low, but kernel pointer disclosure is security-relevant as an exploit helper and should not be blindly auto-closed without confirming product exposure to `/dev/snd/seq`. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: seq: Clear variable event pointer on read [ Upstream Commit: 14fe4f75fd5309d6b75f8e840ada88912b374207 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=14fe4f75fd5309d6b75f8e840ada88912b374207 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=14fe4f75fd5309d6b75f8e840ada88912b374207 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74339 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74339 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:L/I:N/A:N The Best / paranoid CVSS score: 3.3 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).