From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53241][MODERATE REGULAR] ALSA: seq: dummy: fix UMP event stack overread [ Upstream Date: Thu, 25 Jun 2026 09:34:59 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53241 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: a7ef78a2c536242ccb7a4429da01580b2409bb24 List-Id: CVE: CVE-2026-53241 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ALSA: seq: dummy: fix UMP event stack overread [ Upstream Commit: a7ef78a2c536242ccb7a4429da01580b2409bb24 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a7ef78a2c536242ccb7a4429da01580b2409bb24 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53241 Analysis date: Thu, 25 Jun 2026 09:34:59 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline manual review recommended / Ordinary Moderate with actionable info leak concern Manual review required: YES Summary: A local ALSA sequencer user may trigger a UMP event stack overread in the dummy client, potentially leaking adjacent kernel stack data, but the patch does not show a write primitive or direct privilege escalation path. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53241 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53241 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-2026-53241 MODERATE CHECK 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-126;CWE-125;*CWE-200;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 out-of-bounds stack read in the ALSA sequencer dummy port can occur when a UMP event is copied into legacy snd_seq_event sized stack storage while the UMP flag remains set. The subscriber delivery path can then calculate a UMP sized packet and copy bytes past the end of the stack temporary, which may expose adjacent kernel stack data to a local subscriber. For the CVSS the PR:L is used because triggering requires a local process that can access the ALSA sequencer interface and send or route events through the dummy client. The issue is not network reachable. Impact is primarily confidentiality loss from a bounded kernel stack overread. There is no direct write primitive or UAF shown by the code path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Ordinary Moderate with actionable info leak concern (with actual score 3) YES SIMPLEFIX HARDWARE LINUS PACKET INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline manual review recommended / Ordinary Moderate with actionable info leak concern** ## 2. Signal breakdown * Local unprivileged trigger: +1. A local process with access to the ALSA sequencer interface can send or route UMP events through the dummy client. * Confidentiality impact plausible: +1. The bug is an out-of-bounds stack read and may expose adjacent kernel stack bytes through event delivery to subscribers. * Broad/default/common subsystem or broadly deployed exposure: +1 in paranoid scoring only. ALSA sequencer is a common local kernel interface on desktop and audio-enabled systems, but the affected dummy UMP path is more specific and may not be active everywhere. * Limited read-only OOB: +0. The patch shows stack overread, not UAF, OOB write, type confusion, arbitrary write, callback corruption, or object lifetime corruption. * No reliable kernel crash / strong DoS: +0. The described failure mode is overread and possible disclosure, not panic or persistent availability loss. * No privilege escalation plausible signal: +0. There is no write primitive, reclaim primitive, stale callback, refcount takeover, or demonstrated exploit chain. ## 3. Reachability analysis The bug is locally reachable through ALSA sequencer event handling when UMP events can be delivered to the dummy sequencer client. It does not appear network reachable. PR:L is the right practical interpretation because a local user process is needed to access the sequencer device and shape the event flow. Containers or sandboxed environments may reduce exposure if ALSA devices are not passed through, but systems exposing `/dev/snd/seq` to untrusted users or containers should treat it as reachable. The path is common enough for manual review, but not comparable to core networking, page cache, io_uring, or netfilter exposure. ## 4. Severity interpretation This behaves like an ordinary Moderate issue with an actionable confidentiality review requirement. The concrete primitive is a bounded kernel stack overread caused by using legacy-sized stack storage for a larger UMP event while preserving UMP packet semantics. Theoretical usefulness exists because kernel stack disclosure can help other exploit chains, but the patch does not show memory corruption, control-flow influence, write access, or privilege escalation by itself. ## 5. One-sentence report phrase A local ALSA sequencer user may trigger a UMP event stack overread in the dummy client, potentially leaking adjacent kernel stack data, but the patch does not show a write primitive or direct privilege escalation path. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Manual review is recommended because this is a kernel information disclosure primitive from stack overread, even though it is local-only and lacks evidence of memory corruption or direct privilege escalation. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: seq: dummy: fix UMP event stack overread [ Upstream Commit: a7ef78a2c536242ccb7a4429da01580b2409bb24 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a7ef78a2c536242ccb7a4429da01580b2409bb24 Changed files: sound/core/seq/seq_dummy.c sound/core.h sound/initval.h sound/asoundef.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=a7ef78a2c536242ccb7a4429da01580b2409bb24 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53241 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53241 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).