From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64481][MODERATE 7.0] ALSA: hda/cs35l41: Fix firmware load work teardown [ Upstream Date: Sat, 25 Jul 2026 14:15:39 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64481 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 8947215c0136c9d905e4a46d824824f8b48a2e5b List-Id: CVE: CVE-2026-64481 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: ALSA: hda/cs35l41: Fix firmware load work teardown [ Upstream Commit: 8947215c0136c9d905e4a46d824824f8b48a2e5b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8947215c0136c9d905e4a46d824824f8b48a2e5b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64481 Analysis date: Sat, 25 Jul 2026 14:15:39 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: ALSA HDA cs35l41 firmware-load controls and queued work can outlive driver teardown, allowing a local user-triggered firmware-load request to race with unbind or removal and potentially dereference stale driver state, causing a kernel crash and requiring manual review for UAF impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64481 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64481 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 7.0 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-2026-64481 MODERATE 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-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'ALSA HDA cs35l41 firmware load handling can leave ALSA controls and fw_load_work alive across component unbind or device remove. The controls store cs35l41_hda as private data and the firmware load control can queue work before the DSP is initialized when firmware_autostart is disabled. If teardown happens before the queued work runs, the worker or a later control callback can dereference driver state that is no longer valid, creating a race based use-after-free candidate and a likely kernel crash. For the CVSS the PR:L is used because a local user with access to ALSA controls may request firmware loading, while the teardown timing is treated as high complexity rather than as an additional privilege requirement. The issue is not network reachable. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel use-after-free, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES PRINTF-TTY NOMEMCHK ERRORPATH HARDWARE LINUS KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 A local user with access to ALSA mixer controls may request firmware loading through the exposed control path. * Memory corruption, weak/indirect corruption candidate: +1 The bug is a race/lifetime issue where ALSA controls and queued work may dereference driver state after component unbind or device remove. The patch supports a UAF candidate, but does not show controlled reclaim, overwrite, or type confusion. * Real lifetime corruption: +1 The core issue is that `fw_load_work` and ALSA controls can outlive the valid lifetime of `struct cs35l41_hda`. * Reliable kernel crash / strong DoS: +1 A worker running after teardown can dereference invalid driver state, making kernel crash a realistic outcome. * Privileged kernel/device-management lifetime path: +1 in paranoid score The corruption is in a trusted driver teardown and workqueue lifetime path. This is not enough for strong LPE by itself, but it raises manual-review priority. Negative or limiting signals: * Hard or unreliable race / special timing required: -1 Triggering requires a firmware-load request to overlap with component unbind or device removal. * Device/configuration-specific exposure: not scored as broad exposure The issue is limited to systems using the affected Cirrus Logic CS35L41 HDA side codec and relevant firmware loading controls. ## 3. Reachability analysis The bug is local, not network reachable. The likely attacker is a local user or process with access to ALSA controls. The firmware load request may be user-triggerable, but the teardown side usually depends on component unbind, driver removal, device removal, suspend/resume, or other lifecycle events that may not be fully attacker-controlled by an unprivileged user. Namespaces and containers usually do not make this broadly reachable unless the container is granted access to the host audio device and ALSA control interface. This is not a default remote attack surface. Call-site confidence: high. The patch directly shows ALSA controls storing `cs35l41_hda` as private data, explicit removal of controls on unbind, and unconditional cancellation of `fw_load_work` during remove. ## 4. Severity interpretation This is stronger than an ordinary Moderate because it is a kernel lifetime bug with a plausible UAF-style stale callback/workqueue path. Realistic demonstrated impact is local DoS through invalid driver-state dereference. Practical privilege escalation is not demonstrated, because the patch does not show attacker-controlled reclaim, overwrite, type confusion, or callback target control. The paranoid score keeps the issue in manual-review territory because stale kernel driver state is reachable from asynchronous work and ALSA control callbacks after teardown. ## 5. One-sentence report phrase ALSA HDA cs35l41 firmware-load controls and queued work can outlive driver teardown, allowing a local user-triggered firmware-load request to race with unbind or removal and potentially dereference stale driver state, causing a kernel crash and requiring manual review for UAF impact. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a race-based kernel lifetime bug with a plausible use-after-free path through ALSA controls and workqueue teardown, even though current evidence mainly supports local DoS rather than proven privilege escalation. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: hda/cs35l41: Fix firmware load work teardown [ Upstream Commit: 8947215c0136c9d905e4a46d824824f8b48a2e5b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8947215c0136c9d905e4a46d824824f8b48a2e5b Changed files: sound/pci/hda/cs35l41_hda.c sound/pci/hda/cs35l41_hda.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=8947215c0136c9d905e4a46d824824f8b48a2e5b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64481 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64481 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:H/PR:L/UI:N/S:U/C:N/I:N/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: 4 Paranoid ActionableScore: 5 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: YES Published priority for this report (same as in Subject): MODERATE 7.0 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).