From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74331][LOW] firmware_loader: Fix recursive lock in device_cache_fw_images() [ Upstream Date: Sat, 15 Aug 2026 16:43:49 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74331 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: unknown X-AL-KERNEL-Commit: 806cb8fabfde7f830da5ae87777d52fdf50c4774 List-Id: CVE: CVE-2026-74331 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: firmware_loader: Fix recursive lock in device_cache_fw_images() [ Upstream Commit: 806cb8fabfde7f830da5ae87777d52fdf50c4774 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=806cb8fabfde7f830da5ae87777d52fdf50c4774 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74331 Analysis date: Sat, 15 Aug 2026 16:43:49 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A recursive fw_lock acquisition in the firmware loader suspend or hibernation cache path can deadlock under allocation failure conditions, causing a local denial of service without evidence of memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74331 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74331 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-2026-74331 LOW 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:N/I:N/A:H';CWE-667;*CWE-833;**CWE-400;BEST CVSS score: '4.7';DESCR 'A recursive locking deadlock can occur in the firmware loader power management path during suspend or hibernation preparation. device_cache_fw_images held fw_lock while iterating devices and scheduling firmware cache work. Under OOM or allocation failure, async work scheduling can fall back to synchronous execution in the current thread, and the firmware request path can try to acquire fw_lock again. This can deadlock the current suspend or hibernation flow and cause a local denial of service or system hang. For the CVSS the PR:L is used because a local user or local process may be able to trigger suspend or hibernation on some systems, but reliable triggering also depends on memory pressure or allocation failure. The issue is not network reachable. Impact is availability only, with no supported evidence of confidentiality impact, integrity impact, UAF, OOB access, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES LOCK DEADLOCK DANGER HARDWARE LINUS SYZBOT DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 Some systems allow a local user or desktop session to request suspend or hibernation through policy-managed interfaces. * Reliable kernel crash / strong DoS: +1 The bug can deadlock the firmware loader power-management path and hang suspend or hibernation. * Broad/default/common subsystem exposure: +1 Firmware loader and PM suspend paths are common kernel infrastructure. Subtracted signals: * Hard or unreliable race / special timing required: -1 Reliable triggering depends on allocation failure or OOM behavior causing async work to execute synchronously. Not awarded: * No remote reachable signal. The affected path is local power-management handling, not packet or network input. * No memory corruption signal. The patch fixes recursive mutex locking. It does not show UAF, OOB access, double free, type confusion, stale callback, or arbitrary write. * No confidentiality or integrity impact. The supported impact is availability only. ## 3. Reachability analysis A local user or local process may trigger suspend or hibernation on some systems, depending on policy configuration. On servers, suspend and hibernation are often restricted to privileged users or disabled entirely, which lowers practical exposure. Namespaces and containers generally do not provide direct access to host suspend operations, so container reachability is unlikely unless a management interface is delegated. The path is common kernel infrastructure, but exploitation requires a specific allocation-failure fallback during firmware caching, making it condition-dependent. Call-site confidence: high. The commit message gives the full call path from fw_pm_notify to device_cache_fw_images to async fallback to request_firmware and assign_fw. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like availability issue. The realistic impact is a local system hang or failed suspend or hibernation flow. There is no supported evidence of memory corruption, privilege escalation, information disclosure, or security-boundary bypass. Theoretical impact does not extend beyond DoS based on the provided patch and call path. ## 5. One-sentence report phrase A recursive fw_lock acquisition in the firmware loader suspend or hibernation cache path can deadlock under allocation failure conditions, causing a local denial of service without evidence of memory corruption or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is availability-only, condition-dependent, not network reachable, and the patch clearly addresses a recursive locking deadlock rather than a memory lifetime or corruption primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: firmware_loader: Fix recursive lock in device_cache_fw_images() [ Upstream Commit: 806cb8fabfde7f830da5ae87777d52fdf50c4774 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=806cb8fabfde7f830da5ae87777d52fdf50c4774 Changed files: drivers/base/firmware_loader/main.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=806cb8fabfde7f830da5ae87777d52fdf50c4774 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74331 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74331 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:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: unknown 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).