From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64134][LOW] ALSA: pcm: Don't setup bogus iov_iter for silencing Date: Sun, 19 Jul 2026 15:56:24 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64134 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: 41a766c647294842c9b17672449f8e011048cba9 List-Id: CVE: CVE-2026-64134 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: ALSA: pcm: Don't setup bogus iov_iter for silencing Commit: 41a766c647294842c9b17672449f8e011048cba9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=41a766c647294842c9b17672449f8e011048cba9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64134 Analysis date: Sun, 19 Jul 2026 15:56:24 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A local NULL pointer dereference in the ALSA PCM interleaved copy path can occur when PCM silencing reaches the iov_iter transfer path with data NULL, causing a kernel crash on affected RISC-V systems. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64134 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64134 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: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-64134 LOW 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:N/I:N/A:H';**CWE-476;CWE-754;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A NULL pointer dereference in the ALSA PCM interleaved copy path occurs because the iov_iter based transfer path could be reached with data NULL during silence handling. On affected RISC-V systems this can create a bogus iterator and crash the kernel. For the CVSS the PR:L is used because a local user or process needs access to an ALSA PCM device or an audio service path that can trigger PCM silencing. The issue is not network reachable. Impact is denial of service via kernel crash. No privilege escalation or information disclosure primitive is supported by the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES NULLPTR SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown * Local unprivileged trigger: +1 A local user or local process with access to an ALSA PCM device or audio service path may be able to trigger the PCM silencing path. * Reliable kernel crash / strong DoS: +1 The commit explicitly states that the bogus iov_iter setup can cause a NULL dereference on RISC-V, which is a plausible kernel crash. * Rare AND difficult-to-reach subsystem/configuration: -1 in conservative scoring The crash is described as architecture-dependent and currently observed on RISC-V, while most architectures did not show trouble. The affected condition also depends on the PCM silencing path. * No generic memory corruption: +0 The patch shows NULL data handling before do_transfer. It does not show UAF, double free, OOB write, type confusion, refcount misuse, or attacker-controlled overwrite. * No privilege escalation plausible: +0 There is no reclaim primitive, object replacement, write-after-free, callback control, or other LPE-relevant primitive. * No confidentiality or integrity impact: +0 The described failure mode is NULL dereference and crash only. ## 3. Reachability analysis A local user or local service that can open and operate an ALSA PCM device may be able to trigger the affected interleaved PCM silencing path. This is not network reachable. Containers and namespaces generally do not make ALSA devices available unless the device node is deliberately passed through, so container reachability depends on device exposure. The affected subsystem is common on desktop and embedded systems, but the demonstrated crash is architecture-specific to RISC-V and path-specific to silencing with data NULL. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like local DoS issue, not an Important-class vulnerability. The theoretical kernel impact is a NULL dereference crash. The realistic exploitation evidence does not support memory corruption, privilege escalation, information disclosure, or cross-boundary security bypass. The paranoid score keeps the DoS as reliable on affected RISC-V systems but still does not upgrade the bug class. ## 5. One-sentence report phrase A local NULL pointer dereference in the ALSA PCM interleaved copy path can occur when PCM silencing reaches the iov_iter transfer path with data NULL, causing a kernel crash on affected RISC-V systems. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be handled as an auto-close or deferred Moderate unless the affected product exposes ALSA PCM devices to untrusted local users on RISC-V systems where kernel crash availability is considered high priority. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: pcm: Don't setup bogus iov_iter for silencing Commit: 41a766c647294842c9b17672449f8e011048cba9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=41a766c647294842c9b17672449f8e011048cba9 Commit description: At transition to the iov_iter for PCM data transfer, we blindly applied the iov_iter setup also for silencing (i.e. data = NULL), and it leads to a calculation of bogus iov_iter. Fortunately this didn't cause troubles on most of architectures but it goes wrong on RISC-V now, causing a NULL dereference. Handle the NULL data case to treat the silencing in interleaved_copy() for addressing the bug above. noninterleaved_copy() has already the NULL data handling, so it doesn't need changes. Reported-by: Jiakai Xu Closes: https://lore.kernel.org/20260515051516.3103036-1-xujiakai24@mails.ucas.ac.cn Fixes: cf393ba ("ALSA: pcm: Add copy ops with iov_iter") Cc: Link: https://patch.msgid.link/20260517165121.31399-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman Changed files: sound/core/pcm_lib.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=41a766c647294842c9b17672449f8e011048cba9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64134 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64134 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:L/PR:L/UI:N/S:U/C:N/I:N/A:H 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: 1 Paranoid ActionableScore: 2 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).