From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45985][MODERATE 7.0] ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O [ Upstream Date: Wed, 27 May 2026 18:05:00 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45985 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 6 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: 77e407967cd872cd75d7e4a691908e49c8e6b4d4 List-Id: CVE: CVE-2026-45985 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O [ Upstream Commit: 77e407967cd872cd75d7e4a691908e49c8e6b4d4 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=77e407967cd872cd75d7e4a691908e49c8e6b4d4 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45985 Analysis date: Wed, 27 May 2026 18:05:00 -0400 ActionableScore: 6 ActionableScore lower bound: 5 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45985 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45985 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: MODERATE 7.0 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-2026-45985 MODERATE 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:H/I:H/A:L';*CWE-200;CWE-665;CWE-459;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N';BEST CVSS score: '6.5';DESCR 'ext4 can incorrectly pass EXT4_GET_BLOCKS_CONVERT while splitting an unwritten extent before I/O submission. Under a temporary ENOSPC split failure, the on disk extent can be marked written while the extent status tree still treats part of the range as unwritten, and if the later DIO write fails, stale disk data may become visible after the cached extent state is dropped. For the CVSS the PR:L is used because a local user with write access to an affected ext4 file can exercise DIO or writeback paths, although reliable triggering requires specific filesystem state and timing. The issue is not network reachable and does not provide a kernel memory corruption primitive. Impact is primarily confidentiality exposure of stale file data, with integrity concern in the paranoid score due to inconsistent extent state.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 6) MAYBE DISK INIT KPANIC INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=5 1. ActionableScore * Conservative score: 5 * Paranoid score: 6 * Final recommended bucket: **Actionable Moderate at minimum**:: 2. Signal breakdown * Local unprivileged trigger: +1. A local user with write access to an affected ext4 file can exercise DIO/writeback paths. * Confidentiality impact plausible: +1. Stale disk data can become visible after an unwritten extent is incorrectly marked written. * Integrity impact plausible: +1. The on-disk extent state and extent status tree can diverge, affecting file data state. * Important filesystem/storage path: +1. The bug affects ext4 extent handling, DIO, writeback, and unwritten extent conversion. * Security-boundary / sensitive data exposure concern: +1. Stale block exposure can cross file ownership or data-lifetime expectations depending on block reuse and workload. * Hard/special conditions required: -1. Triggering requires within-EOF DIO or writeback with `dioread_nolock`, an unwritten extent split, temporary `ENOSPC`, and later failed DIO. * No kernel memory corruption signal. This is filesystem data exposure/state inconsistency, not UAF, OOB write, or LPE. 3. Reachability analysis The issue is local and requires the attacker to perform writes against an ext4 file in conditions that create or split unwritten extents. It is not network reachable. Containers may be affected if they share an ext4-backed filesystem and can create the necessary DIO/writeback and space-pressure conditions. The conditions are specific and timing/state dependent, but ext4 is a broadly deployed filesystem and stale data exposure is security relevant. 4. Severity interpretation This is an actionable Moderate filesystem confidentiality issue, not a kernel code-execution bug. The realistic impact is exposure of stale file data after inconsistent unwritten extent conversion. The paranoid score adds integrity concern because metadata and extent status can diverge, but there is no evidence of kernel memory corruption or privilege escalation. 5. One-sentence report phrase A local ext4 workload can trigger incorrect unwritten extent conversion during DIO/writeback failure, potentially exposing stale disk data after extent status cache eviction. 6. Manual review recommendation MANUAL CHECK REQUIRED. Stale data exposure in ext4 extent handling can cross file-data confidentiality boundaries and should not be auto-closed, even though exploitation requires specific filesystem state and no kernel memory corruption is shown. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O [ Upstream Commit: 77e407967cd872cd75d7e4a691908e49c8e6b4d4 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=77e407967cd872cd75d7e4a691908e49c8e6b4d4 Changed files: fs/ext4/extents.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=77e407967cd872cd75d7e4a691908e49c8e6b4d4 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45985 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45985 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:L/UI:N/S:U/C:H/I:L/A:N The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L The Best / paranoid CVSS score: 6.5 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: 5 Paranoid ActionableScore: 6 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: MODERATE KPANIC detected for this report: YES Published priority for this report (same as in Subject): MODERATE 7.0 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).