From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98395][LOW] powerpc/entry: Fix irq_soft_mask corruption on replayed interrupt exit [ Upstream Date: Wed, 14 Oct 2026 23:21:06 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98395 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: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 95cd316a896f1c1aa4ee4a817ba3d4691103c81b List-Id: CVE: CVE-2026-98395 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: powerpc/entry: Fix irq_soft_mask corruption on replayed interrupt exit [ Upstream Commit: 95cd316a896f1c1aa4ee4a817ba3d4691103c81b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95cd316a896f1c1aa4ee4a817ba3d4691103c81b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98395 Analysis date: Wed, 14 Oct 2026 23:21:06 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A PowerPC interrupt replay exit can incorrectly clear the PMI disable bit and trigger a kernel warning, but the supplied evidence does not establish memory corruption, attacker-controlled triggering, or a security-boundary impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98395 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98395 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98395 LOW https://www.kernelcve.org/list/?q=CVE-2026-98395 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-682;CWE-703;CWE-755;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A PowerPC interrupt state handling error can clear the IRQS_PMI_DISABLED bit when a replayed interrupt handler exits. The next replayed interrupt is processed without passing through the normal interrupt entry preparation path, leaving irq_soft_mask inconsistent and triggering a kernel warning. The demonstrated condition occurred during early boot on a POWER10 pseries guest while a pending timer interrupt was replayed. For the CVSS the PR:L value is used for the paranoid score because a local execution context is the highest still defensible attacker model, although reliable control by an unprivileged user is not demonstrated. The issue is not network reachable. The confirmed impact is limited availability degradation, while the paranoid impact allows for a boot failure, interrupt handling failure, or system stall. There is no demonstrated UAF, out of bounds access, information disclosure, or arbitrary write primitive. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C and manual review NO. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE WARNONLY HARDWARE LINUS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO ## 1. ActionableScore * Raw conservative score: 0 * Conservative score: 0 * Raw paranoid score: 0 * Paranoid score: 0 * No floor or cap was applied. * Final recommended bucket: **Ordinary Moderate**:: ## 2. Signal breakdown * **+0 WARN_ON continuation:** The demonstrated consequence is a warning caused by an inconsistent PowerPC interrupt soft mask. No panic, host-wide failure, or persistent availability loss is established. * **+0 invalid-state behavior:** Clearing `IRQS_PMI_DISABLED` creates incorrect interrupt bookkeeping, but no independently useful corruption primitive is shown. * **No UAF or lifetime points:** No object is freed, released, or used after its lifetime. * **No memory-corruption points:** There is no OOB read or write, stale pointer, refcount mutation, list corruption, or controlled overwrite. * **No reliable-crash point:** The report demonstrates a warning during boot, not a kernel crash. * **No attacker-reachability points:** No attacker-invocable interface or controllable trigger sequence is established. * **No authorization points:** The change does not alter an access-control decision or capability check. * **No B5-R preservation:** There is no retry-accumulated heap OOB write or later consumption of corrupted heap state. * **No B3-PENDING preservation:** There is no write to shared or file-backed storage. * **No B4-PENDING preservation:** There is no DENY-to-ALLOW authorization transition. * **No negative points applied:** Architecture specificity and interrupt replay were not used as penalties. The lack of attacker reachability already prevents positive scoring, and no narrow race penalty is needed. ## 3. Reachability analysis The observed condition occurs during replay of a pending interrupt on PowerPC, specifically during early boot of a POWER10 pseries guest. The sequence is internal to interrupt exit and replay processing. No syscall, ioctl, network packet, namespace operation, or other attacker-invocable interface is identified. The supplied evidence does not establish that an ordinary user, namespace-capable process, delegated service, guest workload, VMM process, or host administrator can deliberately produce the complete condition. Therefore, host-administrator and namespace requirements remain unknown rather than being assumed. A PowerPC execution environment and the replay path are prerequisites. The behavior is an ordered state-handling defect rather than an established attacker-driven race, so no race penalty or repeatability bonus applies. ## 4. Primitive and severity interpretation The exact primitive is an interrupt-state bookkeeping error. `local_irq_disable()` overwrites `irq_soft_mask` with `IRQS_DISABLED`, removing the `IRQS_PMI_DISABLED` bit before another replayed interrupt is selected. This is neither active structured-object corruption nor fixed stale storage. There is no cleanup UAF, repeated release, refcount mutation, shared-page violation, authorization bypass, or semantic reinterpretation of attacker-controlled state. The demonstrated consequence is a `WARN_ON` caused by `irq_soft_mask` being `0x1` instead of `0x3`. A boot failure, interrupt-handling failure, or system stall is a theoretical concern but is not established by the supplied evidence and is therefore not scored. `PrimitiveClass=CLASS_C` reflects invalid-state and warning behavior without an independently useful corruption primitive. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` are appropriate because no meaningful unresolved memory, ownership, authorization, or security-boundary primitive remains. Likely operational severity is Low-like or ordinary Moderate for affected PowerPC kernels. ## 5. One-sentence report phrase A PowerPC interrupt replay exit can incorrectly clear the PMI disable bit and trigger a kernel warning, but the supplied evidence does not establish memory corruption, attacker-controlled triggering, or a security-boundary impact. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The demonstrated issue is an architecture-specific interrupt-state warning with no established crash, corruption primitive, authorization bypass, or attacker-reachable trigger. ## 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: powerpc/entry: Fix irq_soft_mask corruption on replayed interrupt exit [ Upstream Commit: 95cd316a896f1c1aa4ee4a817ba3d4691103c81b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95cd316a896f1c1aa4ee4a817ba3d4691103c81b Changed files: arch/powerpc/kernel/irq_64.c arch/powerpc/include/asm/entry-common.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=95cd316a896f1c1aa4ee4a817ba3d4691103c81b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98395 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98395 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:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: unknown Paranoid ActionableScore: 0 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).