From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74505][MODERATE 7.0] ALSA: 6fire: Fix UAF at error handling during probe Date: Sat, 15 Aug 2026 14:41:21 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74505 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 49bc7741cd2761c703a292dc69245041ae8a67bd List-Id: CVE: CVE-2026-74505 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ALSA: 6fire: Fix UAF at error handling during probe Commit: 49bc7741cd2761c703a292dc69245041ae8a67bd Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=49bc7741cd2761c703a292dc69245041ae8a67bd Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74505 Analysis date: Sat, 15 Aug 2026 14:41:21 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A pending URB in the ALSA 6fire probe error path may complete after device resources are freed, causing a UAF that is realistically a physical-device-triggered kernel DoS and requires manual review for possible memory corruption impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74505 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74505 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-2026-74505 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'A use-after-free can occur in the ALSA 6fire USB driver during probe error handling because device resources may be freed while a URB is still pending. A malicious or faulty USB device can drive the probe into the error path and later completion of the pending URB may access freed driver state, causing a kernel crash and possibly memory corruption. For the CVSS the PR:N is used for the paranoid score because a physical USB attacker does not need a local account on the victim system to trigger device probing. The issue is not network reachable. Base impact is denial of service, while the paranoid impact uses C:H/I:H/A:H because asynchronous URB UAF is a memory corruption class that can justify manual review for possible privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES USB INIT ERRORPATH UAF HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP 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: * Generic memory corruption: +2 The commit explicitly says a pending URB may survive resource freeing and lead to UAF. * Real lifetime corruption: +1 This is an async USB URB lifetime mismatch in probe error handling. * Reliable kernel crash / strong DoS: +1 A completion path using freed driver state can realistically crash the kernel. * Privileged kernel/device-management memory corruption path: +1 The bug is in USB device probe and URB cleanup logic, a trusted driver/device-management path. * Weak LPE concern: +1, paranoid only UAF in asynchronous URB completion can theoretically become exploitable after heap reuse, but no controlled reclaim, callback control, or overwrite primitive is shown. Subtracted signals: * Physical-only or rare hardware-only condition: -2 Realistic triggering requires a malicious or faulty USB device, USB emulation, or physical/device-level access. * Corruption primitive highly constrained or no demonstrated attacker-controlled reuse: -1 The patch does not show attacker-controlled reclaim, controlled object replacement, arbitrary write, or function pointer control. Call-site confidence: medium. The relevant probe error path and cleanup calls are shown, but the URB completion users and exact freed object accesses are not included in the provided diff. ## 3. Reachability analysis The bug can be triggered during probing of the ALSA 6fire USB device when probe fails after an URB has been submitted but before resources are fully initialized. A malicious or malfunctioning USB device could influence the probe and error path. No local Linux user account is required for a physical USB attacker, so PR:N is reasonable for CVSS physical-vector interpretation. This is not network reachable. Containers and namespaces do not materially lower the requirement because the trigger is device attachment/probing rather than a namespaced userspace API. Exposure is limited because the affected driver and hardware are not broad default attack surfaces. ## 4. Severity interpretation This is not an ordinary bookkeeping bug because the commit explicitly identifies a UAF caused by a pending URB after resource free. Realistic impact is most likely kernel crash or host DoS from a malicious or faulty USB device. Theoretical memory corruption and privilege escalation cannot be excluded because async UAF bugs can sometimes be shaped through heap reuse, but the provided patch does not demonstrate a strong exploit primitive. Therefore it is best treated as Actionable Moderate rather than auto-closed Low or strong Important. ## 5. One-sentence report phrase A pending URB in the ALSA 6fire probe error path may complete after device resources are freed, causing a UAF that is realistically a physical-device-triggered kernel DoS and requires manual review for possible memory corruption impact. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is an explicit UAF in asynchronous USB URB lifetime handling. Even though exposure is physical and exploitability is constrained, kernel UAF bugs should not be auto-closed without manual review. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: 6fire: Fix UAF at error handling during probe Commit: 49bc7741cd2761c703a292dc69245041ae8a67bd Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=49bc7741cd2761c703a292dc69245041ae8a67bd Commit description: Although 6fire driver had a few fixes for dealing with the early error handling during the probe phase, it forgot a pending URB before freeing the resources, which may lead to a UAF. This patch addresses it by doing the almost same cleanup procedure like the normal disconnect phase at the error path. Reported-and-tested-by: Shuangpeng Bai Closes: https://lore.kernel.org/20260724030900.1984491-1-shuangpeng.kernel@gmail.com Cc: Link: https://patch.msgid.link/20260726074821.2288158-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman Changed files: sound/usb/6fire/chip.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=49bc7741cd2761c703a292dc69245041ae8a67bd ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74505 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74505 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:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 6.4 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: NO 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).