From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46052][MODERATE 7.0] ceph: only d_add() negative dentries when they are unhashed [ Upstream Date: Wed, 27 May 2026 15:12:38 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46052 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 83ce43a21bb7df8dd52228afdd918d2d058eefde List-Id: CVE: CVE-2026-46052 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: ceph: only d_add() negative dentries when they are unhashed [ Upstream Commit: 83ce43a21bb7df8dd52228afdd918d2d058eefde Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83ce43a21bb7df8dd52228afdd918d2d058eefde Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46052 Analysis date: Wed, 27 May 2026 15:12:38 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46052 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46052 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-46052 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-664;**CWE-400;*CWE-835;CWE-703;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.6';DESCR 'Ceph can call d_add() on a negative dentry that is already present in the primary dcache hash. Rehashing the same d_hash node can corrupt the hlist bucket and create a self loop, causing __d_lookup() to spin forever and trigger RCU stalls. For the CVSS the PR:L is used because a local process with access to the mounted Ceph filesystem can trigger lookup or atomic_open paths for reused negative dentries without full administrator privileges. The issue is not directly network reachable, although Ceph MDS ENOENT replies participate in one trigger path. Impact is primarily denial of service via CPU stall. Worst case C:L and I:L are kept for manual review sensitivity because kernel dcache metadata is corrupted, but there is no demonstrated arbitrary write or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) MAYBE DANGER DISK HARDWARE LINUS KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: 2. Signal breakdown * Local unprivileged trigger: +1. A local process with access to a mounted Ceph filesystem can trigger lookup or atomic_open paths for reused negative dentries. * Memory corruption, weak/indirect corruption candidate: +1. The bug corrupts VFS dcache hash list metadata by reinserting an already hashed `d_hash` node, potentially creating a self-loop. * Reliable kernel stall / strong DoS: +1. The corrupted hlist can make `__d_lookup()` spin indefinitely and trigger RCU stalls. * Availability impact realistic: +1. The observed impact is CPU stall and system responsiveness degradation. * Important filesystem/storage path: +1. This affects filesystem lookup and dcache behavior in a real Ceph client path. * Rare/configuration-dependent exposure: -1. Practical exposure requires a mounted Ceph filesystem and reused cached negative dentries. * Paranoid weak LPE concern: +1. Kernel metadata corruption is real, but no controlled overwrite, UAF reclaim, arbitrary write, or privilege escalation primitive is demonstrated. 3. Reachability analysis The trigger is local from a process that can access the affected Ceph mount and perform lookups or opens of missing names. A Ceph MDS `ENOENT` response can participate in one path, but this is not a direct unauthenticated remote network vector against the client. Namespaces or containers matter only if untrusted workloads can access the Ceph mount. The path is not default on all Linux systems, but Ceph is a real production filesystem and the affected operation is an ordinary filesystem lookup. 4. Severity interpretation This is more than a simple warning or cleanup issue because it corrupts kernel dcache list metadata. Realistic impact is primarily local denial of service via `__d_lookup()` infinite loop and RCU stalls. Theoretical impact beyond DoS is limited because the corruption is constrained to reinserting the same list node and there is no demonstrated attacker-controlled write or object lifetime primitive. This fits Actionable Moderate rather than clear Important. 5. One-sentence report phrase Ceph can re-add an already hashed negative dentry to the VFS dcache hash, corrupting the hash bucket and allowing a local Ceph filesystem user to trigger `__d_lookup()` stalls and denial of service. 6. Manual review recommendation MANUAL CHECK RECOMMENDED. This is constrained kernel metadata corruption with reliable DoS, but no proven arbitrary write, UAF, information leak, or privilege escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ceph: only d_add() negative dentries when they are unhashed [ Upstream Commit: 83ce43a21bb7df8dd52228afdd918d2d058eefde Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83ce43a21bb7df8dd52228afdd918d2d058eefde Changed files: fs/ceph/dir.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=83ce43a21bb7df8dd52228afdd918d2d058eefde ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46052 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46052 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:L/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:L/I:L/A:H The Best / paranoid CVSS score: 6.6 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: 4 Paranoid ActionableScore: 5 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).