From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64376][LOW] firmware_loader: fix device reference leak in firmware_upload_register() Date: Sat, 25 Jul 2026 12:37:52 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64376 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: 517676ec7dfca064e08f94007a4abd21969de0a0 List-Id: CVE: CVE-2026-64376 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: firmware_loader: fix device reference leak in firmware_upload_register() Commit: 517676ec7dfca064e08f94007a4abd21969de0a0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=517676ec7dfca064e08f94007a4abd21969de0a0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64376 Analysis date: Sat, 25 Jul 2026 12:37:52 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A privileged firmware upload registration failure path can leak embedded device references by freeing the instance directly instead of using device core reference release, causing only low-risk resource leakage in repeated failure scenarios. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64376 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64376 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-2026-64376 LOW CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;*CWE-401;CWE-404;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'firmware_upload_register can take the error path after fw_create_instance has initialized the embedded struct device, but the old cleanup path frees the instance directly instead of dropping the device reference. This leaves device core lifetime accounting unbalanced and can leak references or related resources when alloc_lookup_fw_priv fails during firmware upload registration. For the CVSS the PR:H is selected because reliable triggering normally requires administrative control over driver loading, device probing, or firmware upload provider registration rather than access from an ordinary remote user. The issue is not network reachable and has no evident memory corruption primitive. Impact is limited to availability through resource leakage in repeated failure scenarios.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES LEAK ERRORPATH HARDWARE LINUS NO 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: * +1 Real lifetime corruption: the error path violates device core lifetime rules after `device_initialize()` by freeing `fw_sysfs` directly instead of calling `put_device()`. * +1 Availability impact realistic, paranoid only: repeated privileged triggering could leak device references or related resources over time. Subtracting signals: * -2 Requires admin/root or privileged device-management control in typical deployments: reliable triggering normally requires driver or firmware upload provider registration paths, not ordinary user access. * No remote reachable signal: this is not network-triggerable. * No generic memory corruption signal: the patch indicates a refcount/resource leak, not UAF, OOB write, double free, type confusion, or attacker-controlled overwrite. * No LPE signal: no reclaim, callback control, object replacement, or write primitive is shown. Call-site confidence: high. The relevant allocation, initialization, failure path, and cleanup change are visible in the provided patch. ## 3. Reachability analysis The bug is reachable only through `firmware_upload_register()` failure handling after `fw_create_instance()` succeeds and `alloc_lookup_fw_priv()` fails. In normal deployments this path is controlled by kernel drivers or privileged device-management code. A local unprivileged user is not expected to be able to trigger it directly. Namespaces or containers do not materially lower the privilege requirement unless a product exposes firmware upload provider registration or device probing to a reduced-privilege service, which would be unusual. The path is not remotely reachable and realistic exploitation is limited to repeated privileged failure-path triggering. ## 4. Severity interpretation This behaves like a Low-like or ordinary Moderate cleanup/lifetime bug, not an Important-class vulnerability. The theoretical issue is an unbalanced device reference and resource leak. Realistic impact is limited availability degradation from accumulated leaks. There is no demonstrated memory corruption primitive, privilege escalation path, confidentiality impact, or integrity impact. ## 5. One-sentence report phrase A privileged firmware upload registration failure path can leak embedded device references by freeing the instance directly instead of using device core reference release, causing only low-risk resource leakage in repeated failure scenarios. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is a privileged-only refcount/resource leak with no remote reachability, no concrete memory corruption primitive, and no plausible privilege escalation evidence from the patch context. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: firmware_loader: fix device reference leak in firmware_upload_register() Commit: 517676ec7dfca064e08f94007a4abd21969de0a0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=517676ec7dfca064e08f94007a4abd21969de0a0 Commit description: firmware_upload_register() -> fw_create_instance() -> device_initialize() After fw_create_instance() succeeds, the lifetime of the embedded struct device is expected to be managed through the device core reference counting, since fw_create_instance() has already called device_initialize(). In firmware_upload_register(), if alloc_lookup_fw_priv() fails after fw_create_instance() succeeds, the code reaches free_fw_sysfs and frees fw_sysfs directly instead of releasing the device reference with put_device(). This may leave the reference count of the embedded struct device unbalanced, resulting in a refcount leak. The issue was identified by a static analysis tool I developed and confirmed by manual review. Fix this by using put_device(fw_dev) in the failure path and letting fw_dev_release() handle the final cleanup, instead of freeing the instance directly from the error path. Fixes: 97730bb ("firmware_loader: Add firmware-upload support") Cc: stable@vger.kernel.org Signed-off-by: Guangshuo Li Link: https://patch.msgid.link/20260505091231.607089-1-lgs201920130244@gmail.com Signed-off-by: Danilo Krummrich Signed-off-by: Greg Kroah-Hartman Changed files: drivers/base/firmware_loader/sysfs_upload.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=517676ec7dfca064e08f94007a4abd21969de0a0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64376 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64376 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:H/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.4 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: 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).