From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74734][LOW] firewire: ohci: fix NULL pointer dereference in ar_context_release [ Upstream Date: Wed, 26 Aug 2026 11:44:23 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74734 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: ed5470771c7ed7f959230c4697f316af83426a90 List-Id: CVE: CVE-2026-74734 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: firewire: ohci: fix NULL pointer dereference in ar_context_release [ Upstream Commit: ed5470771c7ed7f959230c4697f316af83426a90 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed5470771c7ed7f959230c4697f316af83426a90 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74734 Analysis date: Wed, 26 Aug 2026 11:44:23 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: YES Summary: A NULL pointer dereference in the FireWire OHCI probe cleanup path can crash the kernel if early PCI initialization fails before AR contexts are initialized, but exploitation normally requires local administrator level device management and no UAF, OOB, info leak, or privilege escalation primitive is shown. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74734 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74734 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-74734 LOW CHECK WITH IMPACT FROM ORIG NN LOW 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-476;CWE-703;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A NULL pointer dereference in the FireWire OHCI probe error path can occur when early PCI initialization fails before AR contexts are initialized. The devres cleanup path calls release_ohci and then ar_context_release, but ar_context_release reads the device pointer through ctx ohci before checking whether ctx buffer existed. This can crash the kernel during probe cleanup and the impact is denial of service only. For the CVSS the PR:L in the paranoid score can be used only for environments where a local low privileged actor can repeatedly trigger device reprobe or driver bind through delegated device management. In typical deployments PR:H is more realistic because probe and PCI driver control require administrator privileges. The issue is not network reachable and does not show a UAF, OOB access, info leak, or write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) SKIP CVE-2026-74734 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE KASAN OOB NULLPTR ERRORPATH KERNEL_PANIC_PLUS_UAF HARDWARE LINUS SYZBOT MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - 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 Conservative signals: * Reliable kernel crash / strong DoS: +1. The patch and KASAN trace show a real NULL pointer dereference in `ar_context_release()` during probe cleanup. * Requires admin/root/CAP_* in typical deployments: -2. Triggering probe, reprobe, bind/unbind, or PCI driver error paths normally requires administrator level device management. * Physical-only or rare hardware-only condition: -2. The issue depends on FireWire OHCI hardware and an early PCI probe failure path. * Rare AND difficult-to-reach subsystem/configuration: -1. FireWire OHCI is not a broad/default attack surface on most modern systems. Paranoid adjustment: * Local low-privileged trigger: +1 only in unusual environments where device reprobe or driver binding is delegated to a less privileged local actor. This is not typical. No added signals for UAF, OOB, arbitrary write, type confusion, info leak, LPE, or ownership/COW bypass. The primitive is a NULL dereference before an initialization check. ## 3. Reachability analysis The bug is local and tied to the FireWire OHCI driver probe error path. A realistic trigger requires a FireWire OHCI device, an early probe failure such as `pcim_enable_device()` or MMIO mapping failure, and execution of the devres cleanup path. In normal deployments, controlling this path requires root or equivalent device management privileges. Containers and namespaces usually do not lower this requirement unless the host explicitly delegates device binding or PCI management. The path is not network reachable. ## 4. Severity interpretation This behaves like a Low or ordinary Moderate availability issue, not an Important class vulnerability. The demonstrated impact is a kernel crash during driver probe cleanup. There is no evidence of memory reuse, stale pointer exploitation, attacker-controlled reclaim, write-after-free, type confusion, callback control, information disclosure, or privilege escalation. The paranoid score only accounts for unusual delegated device-management setups and still remains below actionable Moderate. ## 5. One-sentence report phrase A NULL pointer dereference in the FireWire OHCI probe cleanup path can crash the kernel if early PCI initialization fails before AR contexts are initialized, but exploitation normally requires local administrator level device management and no UAF, OOB, info leak, or privilege escalation primitive is shown. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED. This is a constrained NULL dereference in an uncommon hardware probe error path with typical PR:H reachability and DoS-only impact. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: firewire: ohci: fix NULL pointer dereference in ar_context_release [ Upstream Commit: ed5470771c7ed7f959230c4697f316af83426a90 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed5470771c7ed7f959230c4697f316af83426a90 Changed files: drivers/firewire/ohci.c drivers/base/devres.c drivers/base/dd.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=ed5470771c7ed7f959230c4697f316af83426a90 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74734 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74734 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:H 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: 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).