From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98057][MODERATE REGULAR] ring-buffer: Add checking nr_subbufs to persistent ring buffer validation [ Upstream Date: Sat, 26 Sep 2026 14:36:56 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98057 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: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: f0467190e6a9fc61e343c8064ef16aad513788c3 List-Id: CVE: CVE-2026-98057 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ring-buffer: Add checking nr_subbufs to persistent ring buffer validation [ Upstream Commit: f0467190e6a9fc61e343c8064ef16aad513788c3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f0467190e6a9fc61e343c8064ef16aad513788c3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98057 Analysis date: Sat, 26 Sep 2026 14:36:56 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98057 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98057 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98057 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98057 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';*CWE-20;CWE-129;CWE-125;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.2';DESCR 'Persistent ring buffer validation did not verify that meta nr_subbufs matched the number of allocated pages plus one. Later calculations use nr_subbufs to derive buffer boundaries even though related data is sized from nr_pages plus one, so inconsistent persistent metadata may cause out of bounds metadata processing and a kernel crash while the saved tracing buffer is restored. For the CVSS the PR:H value is used because reliable triggering normally requires administrative control over persistent tracing, reserved memory, or boot configuration. The issue is local and is not network reachable. The base impact is denial of service. Limited confidentiality or integrity impact is retained only in the paranoid score because the affected value controls kernel buffer bounds, but the provided code does not establish an out of bounds write or another strong privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) SKIP CVE-2026-98057 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE TRACE SIMPLEFIX HARDWARE LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 2 * Paranoid score: 2 * No floor or cap changed either score. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Conservative signals: * +1 Memory layout invariant restoration. The patch enforces the required equality between `meta->nr_subbufs` and the allocated layout represented by `nr_pages + 1`. * No negative points. Although the metadata path appears constrained, the supplied context does not positively establish enough reachability details to justify an additional penalty. Paranoid additional signal: * +1 Weak or indirect corruption candidate. An unvalidated `nr_subbufs` controls `buffers_end`, while related data assumes `nr_pages + 1`. This supports possible invalid bounds or structured metadata processing, but not a concrete OOB access. Not awarded: * No reliable-crash point because the supplied commit does not demonstrate an Oops, panic, or specific invalid access. * No UAF, stale lifetime, repeated release, refcount mutation, controlled overwrite, or disclosure is established. * No strong corruption point because the downstream access using the incorrect boundary is not shown. * No confidentiality or integrity points because no data disclosure or write primitive is established. * No local-unprivileged or remote-reachability point because attacker control of persistent metadata is unresolved. * No host-admin penalty because administrative privilege is suggested by typical persistent-tracing setup but is not positively established for the complete trigger. 3. Reachability analysis The malformed value comes from persistent ring-buffer metadata restored during boot or persistent tracing recovery. Administrative configuration of persistent tracing or reserved memory is a plausible prerequisite, but the supplied evidence does not establish who can create the inconsistent metadata or whether it can arise from ordinary runtime activity. No namespace-scoped path, network trigger, attacker-accessible interface, special hardware requirement, or race is shown. Prior privileged setup is plausible but unconfirmed. Therefore both host-admin and namespace privilege requirements remain unknown. 4. Primitive and severity interpretation The exact established defect is missing validation of an allocation and metadata layout invariant. The visible code uses `meta->nr_subbufs` to calculate `buffers_end` even though associated data assumes `nr_pages + 1`. This is passive persistent metadata rather than an active stale object. There is no lifetime violation and no concrete repeated release or refcount operation. The supplied fragment supports invalid-state and possible bounds-processing behavior, so it is CLASS_C. A downstream OOB read or crash is technically plausible but not established by the visible code. An OOB write, controlled target, disclosure, or privilege-escalation primitive would require unsupported additional assumptions. ImportantCandidate is NO because no independently useful corruption or boundary-bypass primitive is demonstrated. AutoDowngradeAllowed is YES because the established issue is validation failure with unresolved but weak downstream consequences. 5. One-sentence report phrase Persistent ring-buffer validation accepts an inconsistent subbuffer count that can produce incorrect buffer boundaries, but the supplied code does not establish a concrete OOB access, disclosure, write, or privilege-escalation primitive. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Review downstream consumers of `buffers_end`, the saved subbuffer array, and `meta->nr_subbufs` to determine whether accepted malformed metadata can cause a concrete OOB read, OOB write, or boot-time kernel crash. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ring-buffer: Add checking nr_subbufs to persistent ring buffer validation [ Upstream Commit: f0467190e6a9fc61e343c8064ef16aad513788c3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f0467190e6a9fc61e343c8064ef16aad513788c3 Changed files: kernel/trace/ring_buffer.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=f0467190e6a9fc61e343c8064ef16aad513788c3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98057 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98057 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:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.2 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: 1 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: 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).