From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64064][MODERATE REGULAR] netfs: Fix netfs_invalidate_folio() to clear dirty bit if all changes gone [ Upstream Date: Sun, 19 Jul 2026 17:30:10 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64064 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 4 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 31ba145faceb378fa01afcb8349e15ea7d95e542 List-Id: CVE: CVE-2026-64064 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: netfs: Fix netfs_invalidate_folio() to clear dirty bit if all changes gone [ Upstream Commit: 31ba145faceb378fa01afcb8349e15ea7d95e542 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=31ba145faceb378fa01afcb8349e15ea7d95e542 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64064 Analysis date: Sun, 19 Jul 2026 17:30:10 -0400 ActionableScore: 4 ActionableScore lower bound: 2 Actionable bucket: Borderline manual review recommended / Ordinary Moderate Manual review required: YES Summary: A local NULL pointer dereference in netfs folio invalidation can occur when truncate removes all dirty data but leaves the folio dirty after detaching private state, allowing a later mmap read to crash the kernel in affected streaming write configurations. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64064 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64064 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 REGULAR 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-2026-64064 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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-476;CWE-754;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A NULL pointer dereference in the netfs folio invalidation path can occur because a folio may remain dirty after truncate removes all dirty data and detaches the netfs_folio private state. A later mmap read can make netfs_read_folio treat the folio as dirty and enter netfs_read_gaps, where the missing private state can cause a kernel oops. For the CVSS the PR:L is used because a local user or process with access to a writable file on an affected netfs mount can trigger the file operation sequence, while no administrative privileges are normally required for the actual read, write, truncate, and mmap operations on that file. The issue is not directly network reachable even though the filesystem backend may be network based. Impact is denial of service via kernel crash. There is no concrete evidence of a use after free, out of bounds access, information leak, or privilege escalation primitive in this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Ordinary Moderate (with actual score 3) SKIP CVE-2026-64064 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 9ebff83e648148b9ece97d4e4890dd84ca54d6ce YES NO NO unknown MAYBE REMOTE WRITE OOB DISK LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 4 * Final recommended bucket: **Borderline manual review recommended / Ordinary Moderate** ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. A local user with access to a writable file on an affected netfs-backed mount can perform write, truncate, mmap, and read operations. * Reliable kernel crash / strong DoS: +1. The commit explicitly describes an oops in `netfs_read_gaps()` after `folio->private` was detached while the folio dirty bit remained set. * Important filesystem/storage path: +1. This is in netfs folio/page-cache style handling, involving dirty state, truncate, mmap read, and filesystem-backed cache semantics. * Rare or difficult-to-reach configuration: -1. The reproducer depends on streaming writes, fscache disabled or suppressed, suitable file layout, and a specific truncate plus mmap sequence. Paranoid additions/changes: * Availability impact realistic: +1. In affected configurations, the sequence appears reproducible and can cause a host kernel oops rather than a harmless warning. * Do not apply the rare configuration penalty in the paranoid score because netfs/page-cache invalidation is an important storage path and the commit says it should be reproducible even without the testing-only source change. Not counted: * No generic memory corruption bonus. The patch shows a stale dirty-state mismatch leading to missing private data and NULL dereference, not UAF reuse, OOB write, double free, type confusion, or controlled overwrite. * No privilege escalation bonus. There is no demonstrated reclaim, write primitive, callback control, or object confusion. * No confidentiality or integrity bonus. The described failure mode is crash/oops only. ## 3. Reachability analysis The trigger is local. A user or process needs access to a writable file on an affected netfs mount and must perform a specific operation sequence involving streaming write, truncate, mmap, and read. Administrative privileges are not required for the file operations themselves if the user already has normal filesystem permissions. The path is not directly network reachable. The backing filesystem may be network-related, but the vulnerable operation is driven by local VFS/netfs page-cache behavior rather than by remote packets. Namespaces and containers may matter if an untrusted container workload can access an affected mounted filesystem. However, this does not look like a container escape primitive by itself. Call-site confidence: high. The commit message describes the concrete path from `netfs_invalidate_folio()` to `netfs_read_folio()` and `netfs_read_gaps()`. ## 4. Severity interpretation This behaves like an ordinary Moderate local DoS with a borderline manual-review reason due to filesystem/page-cache involvement. The realistic impact is kernel oops or crash. Theoretical memory corruption risk is weak because the stale state is a missing `netfs_folio` private structure after detach, and the described consumer dereferences an expected pointer rather than reusing attacker-controlled freed memory. It should not be treated as Important based on the provided patch. There is no supported LPE, arbitrary write, page-cache ownership violation, or sensitive data exposure primitive. ## 5. One-sentence report phrase A local NULL pointer dereference in netfs folio invalidation can occur when truncate removes all dirty data but leaves the folio dirty after detaching private state, allowing a later mmap read to crash the kernel in affected streaming write configurations. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Manual review is recommended because the issue affects netfs folio/page-cache state and can cause a kernel oops, but the current evidence supports local DoS only and does not show memory corruption or privilege escalation. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfs: Fix netfs_invalidate_folio() to clear dirty bit if all changes gone [ Upstream Commit: 31ba145faceb378fa01afcb8349e15ea7d95e542 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=31ba145faceb378fa01afcb8349e15ea7d95e542 Changed files: fs/netfs/misc.c include/trace/events/netfs.h 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=31ba145faceb378fa01afcb8349e15ea7d95e542 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64064 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64064 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: 2 Paranoid ActionableScore: 4 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: NO Published priority for this report (same as in Subject): MODERATE REGULAR 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).