From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74308][LOW] ext4: fix kernel BUG in ext4_write_inline_data_end [ Upstream Date: Sun, 16 Aug 2026 03:32:15 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74308 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: unknown X-AL-KERNEL-Commit: 260830a9a706f5d335398236fc788ce32f220de1 List-Id: CVE: CVE-2026-74308 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: ext4: fix kernel BUG in ext4_write_inline_data_end [ Upstream Commit: 260830a9a706f5d335398236fc788ce32f220de1 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=260830a9a706f5d335398236fc788ce32f220de1 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74308 Analysis date: Sun, 16 Aug 2026 03:32:15 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: YES Summary: An ext4 journalled inline data write can incorrectly enter the inline write completion path after EXT4_STATE_MAY_INLINE_DATA was cleared, triggering a kernel BUG and local denial of service under specific filesystem state and mount conditions. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74308 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74308 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-2026-74308 LOW CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-617;CWE-754;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'An ext4 journalled inline data write can reach a kernel BUG because ext4_journalled_write_end() may call ext4_write_inline_data_end() after EXT4_STATE_MAY_INLINE_DATA was cleared while EXT4_INODE_INLINE_DATA is still set. This can happen after a failed inline data to extent conversion such as an ENOSPC case, where the next write no longer prepares or expands the inline data xattr but the journalled write end path still attempts the inline write completion. For the CVSS the PR:L is used because a local user generally needs the ability to write to an affected ext4 filesystem, while the mount configuration itself is normally administrator controlled. The issue is not network reachable and requires local filesystem operations on a system using ext4 inline data with data journal mode. Impact is denial of service via kernel BUG or kernel crash, with no concrete evidence of information disclosure or privilege escalation from this patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES DANGER DISK SIMPLEFIX LINUS SYZBOT DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 A local user who can write to an affected ext4 filesystem may be able to reach the write path. * Reliable kernel crash / strong DoS: +1 The described failure reaches a BUG_ON in ext4_write_inline_data(), which can crash the kernel. * Important filesystem/storage path: +1 ext4 write handling is an important filesystem path. * Broad/default/common subsystem: +1 ext4 is broadly deployed, although this specific path depends on non-default options. Negative signals: * Hard or special trigger conditions: -1 The crash requires a specific state sequence: data=journal, inline data, failed inline-to-extent conversion such as ENOSPC, then a later write. * Legacy / non-default execution mode: -1 The affected path requires data=journal and inline data behavior, which is not the default ext4 configuration in typical deployments. Not awarded: * No generic memory corruption score. The patch prevents reaching a BUG_ON and does not show UAF, double free, OOB write, type confusion, or arbitrary write. * No confidentiality or integrity impact. The demonstrated primitive is kernel crash only. * No additional availability point. The reliable crash signal already accounts for the DoS impact. * No filesystem metadata corruption signal. The patch context shows an assertion failure, not persistent metadata corruption. Call-site confidence: high. The changed call site and failure condition are directly present in the patch context. ## 3. Reachability analysis The bug is locally reachable through filesystem write operations on an affected ext4 filesystem. A normal local user may trigger it if they can write to the relevant filesystem, but the required mount configuration is normally controlled by an administrator. Namespaces or containers only matter if the container can write to a host-backed affected ext4 filesystem. The bug is not network reachable. Realistic exploitation requires a system using ext4 inline data together with data=journal and a reproducible failed conversion state, such as ENOSPC during inline data expansion. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like local DoS issue, not an Important-class kernel vulnerability. The theoretical impact is a kernel BUG and crash. There is no realistic evidence in the patch of memory corruption beyond the assertion condition, no stale pointer lifetime issue, no attacker-controlled overwrite, and no privilege escalation primitive. ## 5. One-sentence report phrase An ext4 journalled inline data write can incorrectly enter the inline write completion path after EXT4_STATE_MAY_INLINE_DATA was cleared, triggering a kernel BUG and local denial of service under specific filesystem state and mount conditions. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED. This appears to be a local DoS-only BUG_ON issue with non-default filesystem conditions and no supported memory corruption or privilege escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ext4: fix kernel BUG in ext4_write_inline_data_end [ Upstream Commit: 260830a9a706f5d335398236fc788ce32f220de1 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=260830a9a706f5d335398236fc788ce32f220de1 Changed files: fs/ext4/inode.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=260830a9a706f5d335398236fc788ce32f220de1 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74308 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74308 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:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: unknown 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).