From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72403][LOW] ALSA: FCP: Fix NULL pointer dereference in interface lookup [ Upstream Date: Sat, 15 Aug 2026 21:28:41 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72403 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: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: f28d7b5f1578a7501ab17b10643ed1e4f729187e List-Id: CVE: CVE-2026-72403 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: ALSA: FCP: Fix NULL pointer dereference in interface lookup [ Upstream Commit: f28d7b5f1578a7501ab17b10643ed1e4f729187e Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f28d7b5f1578a7501ab17b10643ed1e4f729187e Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72403 Analysis date: Sat, 15 Aug 2026 21:28:41 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72403 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72403 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-2026-72403 LOW CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;*CWE-20;CWE-754;BEST CVSS score: '4.6';DESCR 'A NULL pointer dereference in the ALSA/FCP USB driver occurs because fcp_find_fc_interface() can select a vendor specific interface and then read endpoint 0 without checking that any endpoint descriptors exist. A malformed physical USB device can expose bNumEndpoints as 0, causing get_endpoint(..., 0) to produce an invalid endpoint descriptor pointer and usb_endpoint_num() to dereference it. For the CVSS the PR:N is used because the attacker does not need an authenticated local account on the target system, only the ability to present a crafted USB device. The attack vector is physical rather than network reachable. Impact is denial of service via kernel crash or oops, with no supported confidentiality or integrity impact from the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES NULLPTR USB SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 1. **ActionableScore** * Conservative score: **0** * Paranoid score: **1** * Final recommended bucket: **Ordinary Moderate / Low-like**:: 2. **Signal breakdown** Triggered signals: * Reliable kernel crash / strong DoS: **+1** The malformed USB device can cause a NULL pointer dereference in `usb_endpoint_num()` after `get_endpoint(..., 0)` is used on an interface with `bNumEndpoints == 0`. * Physical-only or rare hardware-only condition: **-2** The attacker must present a crafted physical USB device or equivalent USB emulation to the target. This is not remotely network reachable. Paranoid-only interpretation: * Firmware-mediated external influence: **+1** A malicious USB device controls descriptors consumed by the kernel driver. This is still physical/device-mediated, not network reachable. Not awarded: * Generic memory corruption: **+0** This is a NULL pointer dereference, not UAF, OOB write, double free, type confusion, or arbitrary write. * Privilege escalation plausible: **+0** No reclaim primitive, writable corruption sink, callback control, refcount abuse, or attacker-controlled object replacement is shown. * Confidentiality / Integrity impact: **+0** The patch supports DoS only. * Availability impact realistic: **+0 additional** Availability is already counted through the reliable crash signal. No persistent filesystem, storage, or cross-workload impact is indicated. Call-site confidence: **high**. The changed check is directly adjacent to the unsafe endpoint access and the commit message describes the dereference path. 3. **Reachability analysis** The bug is triggered by a malformed USB device exposing a vendor-specific interface with zero endpoint descriptors. No local account is required on the victim in CVSS-style terms, but the attacker needs physical USB access or a way to emulate a USB device to the host. Namespaces and containers do not materially reduce the required access because the trigger is device enumeration in the host kernel. The affected driver path is not a network path and is not normally exposed to remote attackers. Realistic exploitation is a physical DoS scenario against systems that accept untrusted USB devices. 4. **Severity interpretation** This behaves like an ordinary Moderate or Low-like kernel issue rather than an Important-class vulnerability. The theoretical impact is a kernel oops or crash from a NULL pointer dereference. There is no evidence of a memory corruption primitive that could support privilege escalation, information disclosure, or integrity compromise. The physical-only reachability strongly limits practical exposure. 5. **One-sentence report phrase** A malformed physical USB device can trigger a NULL pointer dereference in the ALSA/FCP interface lookup path by exposing a vendor-specific interface without endpoints, causing a local physical denial of service without evidence of privilege escalation or data exposure. 6. **Manual review recommendation** **NO MANUAL CHECK NEEDED** This is a physical USB NULL pointer dereference with DoS-only impact, no supported memory corruption primitive beyond invalid dereference, no network reachability, and a low ActionableScore. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: FCP: Fix NULL pointer dereference in interface lookup [ Upstream Commit: f28d7b5f1578a7501ab17b10643ed1e4f729187e Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f28d7b5f1578a7501ab17b10643ed1e4f729187e Changed files: sound/usb/fcp.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=f28d7b5f1578a7501ab17b10643ed1e4f729187e ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72403 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72403 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: Not available The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.6 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: 0 Paranoid ActionableScore: 1 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).