From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64217][IMPORTANT] netfs: Fix overrun check in netfs_extract_user_iter() [ Upstream Date: Fri, 24 Jul 2026 12:53:59 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64217 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 8 X-AL-KERNEL-ActionableScore-Lower: 6 X-AL-KERNEL-Commit: 00efe58bbdcc93272d579ca24bfc912563f4a204 List-Id: CVE: CVE-2026-64217 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: netfs: Fix overrun check in netfs_extract_user_iter() [ Upstream Commit: 00efe58bbdcc93272d579ca24bfc912563f4a204 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=00efe58bbdcc93272d579ca24bfc912563f4a204 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64217 Analysis date: Fri, 24 Jul 2026 12:53:59 -0400 ActionableScore: 8 ActionableScore lower bound: 6 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A local memory corruption issue in `netfs_extract_user_iter()` can occur when `iov_iter_extract_pages()` overfills the expected byte or page bounds, allowing corrupted page state to influence bvec iterator construction and potentially causing kernel crash or worse impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64217 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64217 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: IMPORTANT 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-2026-64217 IMPORTANT CHECK WITH IMPACT FROM ORIG NN MODERATE 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:H';*CWE-787;CWE-119;*CWE-20;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A memory corruption issue in netfs_extract_user_iter can occur when iov_iter_extract_pages overfills the expected page or byte limits and the resulting pages are still considered while constructing the final iterator. A local user process that can reach the affected netfs user iterator path through file I/O on a netfs backed mount may be able to trigger a kernel crash and potentially corrupt kernel memory. For the CVSS the PR:L is used because reliable triggering requires local code execution or a local process context, but it does not necessarily require administrator privileges. The issue is not directly network reachable as an incoming packet attack, although netfs itself may be used with remote filesystems. Impact is at least local denial of service via kernel crash and in the paranoid case may include confidentiality and integrity impact due to kernel memory corruption, so privilege escalation risk should be manually reviewed.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) SKIP CVE-2026-64217 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 85dd2c8ff368b1446be9febde84afe1d7aec4261 YES NO NO unknown MAYBE REMOTE WRITE OOB DANGER DISK SIMPLEFIX LINUS KPANIC MEMORY KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=6 ## 1. ActionableScore * Conservative score: 6 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown * Local unprivileged trigger: +1. A local user process may reach this through file I/O on a mounted netfs-backed filesystem. * Constrained kernel buffer overwrite / weak-indirect corruption candidate: +1. The patch explicitly states that if `iov_iter_extract_pages()` overfills `pages[]`, memory corruption has already happened, but the overwritten payload appears to be page-pointer based and not clearly an arbitrary attacker-chosen write. * Memory layout invariant restoration: +1. The fix restores consistency between `count`, `offset`, `cur_npages`, `npages`, and `max_pages` during bvec iterator construction. * Weak LPE concern: +1. Kernel memory corruption in a filesystem iterator path creates plausible escalation concern, but no concrete reclaim, arbitrary write, callback control, or type confusion primitive is shown. * Availability impact realistic: +1. A corrupted iterator or bvec state can plausibly lead to kernel crash or unsafe cleanup behavior. * Important filesystem/storage path: +1. This is in netfs iterator construction, affecting filesystem I/O paths. * Paranoid additional C/I impact: +2. Because the patch explicitly acknowledges memory corruption, confidentiality and integrity impact are defensible for manual-review sensitivity, even though exploitation beyond DoS is not demonstrated. ## 3. Reachability analysis The likely trigger is local file I/O through a netfs-backed mount. This should be treated as PR:L, not PR:N, because a local process context is required. No direct incoming network packet trigger is shown, even though netfs may be used with remote filesystems. Containers or namespaces may matter if an untrusted workload can access an affected mounted filesystem, but mounting or configuring the filesystem itself is typically privileged. Call-site confidence: medium, because the patch shows the vulnerable helper logic but not all callers. ## 4. Severity interpretation This is not an ordinary Moderate cleanup issue. The commit explicitly says that an overfill means memory corruption has already occurred, and the fix prevents corrupted page entries from being included in the constructed iterator. Realistic demonstrated impact is closest to local DoS or kernel memory corruption. Privilege escalation is not proven, but the filesystem iterator and bvec construction context makes this an actionable manual-review case. ## 5. One-sentence report phrase A local memory corruption issue in `netfs_extract_user_iter()` can occur when `iov_iter_extract_pages()` overfills the expected byte or page bounds, allowing corrupted page state to influence bvec iterator construction and potentially causing kernel crash or worse impact. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. The patch explicitly describes memory corruption in a filesystem I/O path, and the conservative score is already in Actionable Moderate range while the paranoid score reaches Strong Important candidate range. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfs: Fix overrun check in netfs_extract_user_iter() [ Upstream Commit: 00efe58bbdcc93272d579ca24bfc912563f4a204 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=00efe58bbdcc93272d579ca24bfc912563f4a204 Changed files: fs/netfs/iterator.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=00efe58bbdcc93272d579ca24bfc912563f4a204 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64217 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64217 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:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7 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: 6 Paranoid ActionableScore: 8 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).