From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53192][MODERATE 7.0] ALSA: timer: Fix UAF at snd_timer_user_params() Date: Thu, 25 Jun 2026 07:35:01 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53192 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: 92ad2d7f80cad43b046f093e808e11fe919d304a List-Id: CVE: CVE-2026-53192 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: ALSA: timer: Fix UAF at snd_timer_user_params() Commit: 92ad2d7f80cad43b046f093e808e11fe919d304a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=92ad2d7f80cad43b046f093e808e11fe919d304a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53192 Analysis date: Thu, 25 Jun 2026 07:35:01 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A race in ALSA timer `SNDRV_TIMER_IOCTL_PARAMS` handling can access a timer instance while the associated timer object is being released, causing a local use-after-free with realistic kernel crash impact and possible but unproven privilege-escalation concern. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53192 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53192 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-2026-53192 MODERATE CHECK 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-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'ALSA timer has a local race based use after free in snd_timer_user_params() because SNDRV_TIMER_IOCTL_PARAMS was not protected by register_mutex while timer teardown can detach and free the timer object. A local process that can open the ALSA timer device can race this ioctl with closing or releasing a userspace timer and can reach stale timer instance state. For the CVSS the PR:L is used because reliable triggering requires local code execution and access to the ALSA timer interface, but it does not require full administrator privileges in common desktop or audio group configurations. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to UAF memory corruption, so manual review is required.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES INIT RACE UAF HARDWARE LINUS KPANIC NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 A local process that can access the ALSA timer interface can issue `SNDRV_TIMER_IOCTL_PARAMS`. * Memory corruption, weak primitive: +1 The commit explicitly describes a race leading to use-after-free, but the patch does not show attacker-controlled reclaim, overwrite, callback dispatch, or type confusion. * Real lifetime corruption: +1 The bug is a timer object lifetime race between `snd_timer_user_params()` and timer release through `snd_timer_free()`. * Reliable kernel crash / strong DoS: +1 A UAF in a kernel ioctl path is sufficient for realistic local crash risk. * Broad/default/common subsystem exposure: +1 in paranoid score ALSA timer support is commonly present on desktop and audio-enabled systems, although access depends on device permissions and configuration. Subtract: * Hard or unreliable race / special timing required: -1 Exploitation requires racing an ioctl against timer object release. Not awarded: * No remote/network trigger. * No strong LPE bonus because the patch does not show reclaim control, stale object replacement, write-after-free, type confusion, callback control, or refcount takeover. * No confidentiality or integrity impact in the conservative score. ## 3. Reachability analysis The bug is locally reachable through the ALSA timer userspace interface. In typical deployments, the attacker needs local code execution and permission to open the relevant ALSA timer device, which may be granted to desktop users or members of audio-related groups. Containers usually cannot reach this path unless sound devices are passed through or device cgroup policy allows access. The path is not network reachable. Practical triggering requires a race between parameter ioctl handling and timer object teardown, so reliability is lower than a simple deterministic NULL dereference. ## 4. Severity interpretation This is more than an ordinary Moderate because it is an explicit kernel UAF in a local ioctl path. Conservatively, it behaves like a local DoS with weak memory-corruption evidence. Paranoid handling raises it to Actionable Moderate because local kernel UAF bugs are often underestimated during early triage, even though this patch does not demonstrate a concrete privilege-escalation primitive. It should not be treated as a strong Important issue solely from the patch, but it should not be auto-closed. ## 5. One-sentence report phrase A race in ALSA timer `SNDRV_TIMER_IOCTL_PARAMS` handling can access a timer instance while the associated timer object is being released, causing a local use-after-free with realistic kernel crash impact and possible but unproven privilege-escalation concern. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch explicitly fixes a race-based UAF in a local kernel userspace API. The demonstrated primitive is weak, but UAF lifetime bugs require manual review to assess reclaim possibilities, object layout, and whether the stale timer instance can be abused beyond DoS. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: timer: Fix UAF at snd_timer_user_params() Commit: 92ad2d7f80cad43b046f093e808e11fe919d304a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=92ad2d7f80cad43b046f093e808e11fe919d304a Commit description: At releasing a timer object, e.g. when a userspace timer (CONFIG_SND_UTIMER) gets closed and snd_timer_free() is called, it tries to detach the timer instances and release the resources. However, it's still possible that other in-flight tasks are holding the timer instance where the to-be-deleted timer object is associated, and this may lead to racy accesses. Fortunately, most of ioctls dealing with the timer instance list already have the protection with register_mutex, and this also avoids such races. But, SNDRV_TIMER_IOCTL_PARAMS isn't protected, hence the concurrent ioctl may lead to use-after-free. This patch just adds the guard with register_mutex to protect snd_timer_user_params() for covering the code path as a quick workaround. It's no hot-path but rather a rarely issued ioctl, so the performance penalty doesn't matter. Reported-by: Kyle Zeng Tested-by: Kyle Zeng Cc: Link: https://patch.msgid.link/20260606161145.1933447-2-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman Changed files: sound/core/timer.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=92ad2d7f80cad43b046f093e808e11fe919d304a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53192 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53192 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:L/I:L/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).