From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-43066][LOW] ext4: fix iloc.bh leak in ext4_fc_replay_inode() error paths [ Upstream Date: Tue, 09 Jun 2026 17:46:50 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-43066 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: 0 X-AL-KERNEL-Commit: 0892f12cd49fde5d5db68137923db107f894f3a3 List-Id: CVE: CVE-2026-43066 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: ext4: fix iloc.bh leak in ext4_fc_replay_inode() error paths [ Upstream Commit: 0892f12cd49fde5d5db68137923db107f894f3a3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0892f12cd49fde5d5db68137923db107f894f3a3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43066 Analysis date: Tue, 09 Jun 2026 17:46:50 -0400 ActionableScore: 2 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like, autoclose candidate Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43066 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43066 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-2026-43066 LOW CHECK 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:L/A:H';*CWE-772;*CWE-401;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.3';DESCR 'ext4 fast commit replay can leak a buffer_head reference because ext4_fc_replay_inode may jump to error paths without releasing iloc.bh after ext4_get_fc_inode_loc. The same function also returned success even when some replay operations failed, which can hide recovery errors from higher layers. For the CVSS the PR:L in the paranoid score is used only for environments where an untrusted local user can influence ext4 mount or recovery through delegated mount access, removable media handling, or a privileged helper. In the normal case PR:H is more realistic because mounting or recovering an ext4 filesystem requires administrative privileges. The issue is local and not network reachable. Impact is mainly resource exhaustion and possible filesystem recovery inconsistency, not privilege escalation or direct memory corruption.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, autoclose candidate (with actual score 1) YES DISK SIMPLEFIX LEAK ERRORPATH INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=0 1. ActionableScore * Conservative score: 0 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like, autoclose candidate**:: 2. Signal breakdown * Important filesystem/storage path: +1. The bug is in ext4 fast commit recovery, which is an important filesystem integrity and recovery path. * Availability impact realistic: +1 in the paranoid view. A leaked `buffer_head` reference during repeated failed recovery attempts could contribute to resource leakage or recovery disruption, but the patch does not show an immediate reliable system-wide crash. * Local unprivileged trigger: +1 only in the paranoid view. This applies only if an unprivileged user can influence mounting or recovery through removable media handling, delegated mount workflows, or a privileged helper. * Requires admin/root in typical deployments: -2 in the conservative view. Mounting or recovering an ext4 filesystem normally requires administrative privileges. * Hard or special condition required: -1. The leak occurs only on specific error paths during fast commit replay, not on ordinary file operations. * No memory corruption signal. The patch fixes a missing `brelse()` and error propagation, not UAF, OOB write, double free, type confusion, or page-cache corruption. * No privilege escalation signal. There is no demonstrated reclaim primitive, arbitrary write, metadata overwrite, credential impact, or security-boundary bypass. 3. Reachability analysis Typical triggering requires mounting or recovering an ext4 filesystem with fast commit replay and hitting one of the affected error paths. In normal deployments this is a privileged local operation, usually root or a mount helper. Containers and namespaces usually do not make this broadly reachable unless the environment delegates real filesystem mounting or processes attacker-supplied block images. The path is not network reachable. Realistic exploitation conditions are narrow and mostly amount to resource leakage or hidden recovery failure, not direct compromise. 4. Severity interpretation This behaves like an ordinary Moderate or Low-like filesystem recovery bug. The theoretical impact is resource exhaustion or filesystem recovery inconsistency if the error path is repeatedly reached. The realistic evidence does not support memory corruption, privilege escalation, confidentiality impact, or attacker-controlled integrity corruption of filesystem metadata. The issue should not be treated as an Important candidate based on the provided patch. 5. One-sentence report phrase An ext4 fast commit recovery error path could leak an `iloc.bh` buffer_head reference and hide replay errors, causing possible resource leakage or recovery inconsistency during privileged local mount or recovery operations. 6. Manual review recommendation NO MANUAL CHECK NEEDED. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED. The issue is a constrained reference leak in privileged ext4 recovery paths with no concrete memory corruption or privilege escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ext4: fix iloc.bh leak in ext4_fc_replay_inode() error paths [ Upstream Commit: 0892f12cd49fde5d5db68137923db107f894f3a3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0892f12cd49fde5d5db68137923db107f894f3a3 Changed files: fs/ext4/fast_commit.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=0892f12cd49fde5d5db68137923db107f894f3a3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43066 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43066 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:L/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H The Best / paranoid CVSS score: 5.3 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: 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).