From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-92494][LOW] ext4: fix buffer_head leak in ext4_init_orphan_info [ Upstream Date: Fri, 18 Sep 2026 02:12:37 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-92494 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: unknown X-AL-KERNEL-Commit: a9a6ec1298f9bc134b2c5db27d25bb10603b7113 List-Id: CVE: CVE-2026-92494 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: ext4: fix buffer_head leak in ext4_init_orphan_info [ Upstream Commit: a9a6ec1298f9bc134b2c5db27d25bb10603b7113 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a9a6ec1298f9bc134b2c5db27d25bb10603b7113 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92494 Analysis date: Fri, 18 Sep 2026 02:12:37 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-92494 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92494 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-2026-92494 LOW https://www.kernelcve.org/list/?q=CVE-2026-92494 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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'A buffer_head reference leak in ext4_init_orphan_info() can occur when an ext4 orphan file block is read successfully but then fails bad magic/checksum validation. The error path previously skipped the current buffer_head and released only earlier entries, leaving a kernel reference leaked after the failed mount path. For the CVSS the PR:H is used because reliable triggering normally requires the ability to mount or supply a crafted ext4 filesystem image on the target. The issue is not network reachable and does not indicate a UAF, OOB access, or arbitrary write primitive. Impact is denial of service through gradual kernel memory/resource exhaustion after repeated mount attempts, not privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES DISK SIMPLEFIX LEAK ERRORPATH LINUS YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=NONE RealUAF=NO HostAdminRequired=YES NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 1 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate**:: No floor or cap changed the score. 2. Signal breakdown Positive signals: * +1 Concrete persistent kernel resource/reference leak. `ext4_bread()` returns a `buffer_head` reference and the old error path skipped the currently loaded entry after bad magic or checksum validation failed. * +1 Resource exhaustion potential. Repeated failed mount attempts against a malformed ext4 filesystem with orphan file blocks could accumulate leaked `buffer_head` references. * +1 Important filesystem/storage path. The code is in ext4 orphan file initialization during mount, but the established defect is still a reference leak rather than filesystem ownership corruption or metadata overwrite. Negative signals: * -2 Host-admin-equivalent triggering requirement. Reliable triggering normally requires mounting or providing a crafted ext4 filesystem image to the kernel, which is host-admin-controlled in normal Linux deployments. Non-awarded signals: * No UAF or double release is established. * No OOB read or OOB write is established. * No arbitrary write or controlled reclaim is demonstrated. * No confidentiality or integrity impact is awarded. * No security-boundary bypass is established. * No remote reachability is established. * No extra availability point is awarded beyond the resource-exhaustion potential. 3. Reachability analysis The practical trigger is a malformed ext4 filesystem whose orphan file block is read successfully but fails magic or checksum validation. A local attacker would normally need host-admin-equivalent ability to mount the crafted filesystem image or otherwise make the host mount it. The complete trigger is not shown to be namespace-scoped because ext4 mounting is not generally available to ordinary unprivileged users inside attacker-created namespaces. There is no network path in the patch. No race or special timing is required. No special hardware is required. 4. Primitive and severity interpretation The exact primitive is a leaked `buffer_head` reference on an ext4 mount error path. This is a resource/reference leak, not stale post-lifetime use. The skipped object is not used after free, and the patch does not show a second `brelse()` on the same dangling object. The demonstrated consequence is gradual kernel resource or memory pressure if the failing path is repeated. The speculative worst case is local DoS through exhaustion, but there is no supported path to privilege escalation, information disclosure, arbitrary write, or filesystem ownership bypass. PrimitiveClass is NONE because no meaningful corruption, lifetime misuse after free, authorization bypass, or ownership violation is established. ImportantCandidate is NO because the issue is host-admin-gated and resource-leak-only. AutoDowngradeAllowed is YES because no unresolved kernel-corruption or security-boundary primitive remains. 5. One-sentence report phrase A buffer_head reference leak in ext4_init_orphan_info can occur on malformed orphan file blocks and may cause gradual local resource exhaustion after repeated privileged mount attempts, but it does not establish memory corruption, privilege escalation, or network reachability. 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: this is a concrete but narrow resource/reference leak with host-admin-gated reachability and no UAF, OOB access, arbitrary write, authorization bypass, or plausible LPE primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ext4: fix buffer_head leak in ext4_init_orphan_info [ Upstream Commit: a9a6ec1298f9bc134b2c5db27d25bb10603b7113 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a9a6ec1298f9bc134b2c5db27d25bb10603b7113 Changed files: fs/ext4/orphan.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=a9a6ec1298f9bc134b2c5db27d25bb10603b7113 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-92494 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92494 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:L/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: unknown 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).