From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98399][LOW] s390/ipl: Fix NULL deref in dump_reipl without re-IPL parm block [ Upstream Date: Thu, 15 Oct 2026 11:03:31 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98399 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: 41647864e62b28388ecccc23a82f0e0a091f4ef2 List-Id: CVE: CVE-2026-98399 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: s390/ipl: Fix NULL deref in dump_reipl without re-IPL parm block [ Upstream Commit: 41647864e62b28388ecccc23a82f0e0a091f4ef2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=41647864e62b28388ecccc23a82f0e0a091f4ef2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98399 Analysis date: Thu, 15 Oct 2026 11:03:31 -0400 ActionableScore: 0 ActionableScore lower bound: unknown 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-2026-98399 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98399 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-2026-98399 LOW https://www.kernelcve.org/list/?q=CVE-2026-98399 CHECK WITH IMPACT FROM ORIG NN MODERATE | 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:H/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-252;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'The s390 stand alone dump path can dereference a NULL re IPL parameter block when the system was booted without an IPL parameter block, such as through HMC FTP boot or QEMU direct kernel boot. Address zero may contain readable lowcore data, so the failure does not always cause an immediate fault. It can instead store a zero IPL parameter block address and leave the stand alone dumper in disabled wait after the dump, preventing the expected automatic re IPL. For the CVSS the PR:H is selected because configuring and invoking the dump and re IPL workflow normally requires administrative control. The issue is local and is not network reachable. Impact is limited to availability during an exceptional shutdown or dump workflow, with no supported UAF, information disclosure, controlled memory corruption, or privilege escalation primitive. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 4.1 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to LOW because the CVSS score, vector or bug class threshold rule was applied. 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. Exact triggered rule markers were DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH. The independent weaker Aegis shadow evaluated CVSS 2.0 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 OOB SIMPLEFIX HARDWARE DEBUGFS LINUS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO 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 Invalid pointer read: `reipl_block_actual` can be NULL, and the code reads `reipl_block_actual->hdr.len` and passes the null address to `cksm()`. This is a weak invalid-read or fault primitive, not a write or lifetime violation. * +0 Reliable kernel crash not awarded: the commit says address zero may contain readable lowcore data, and the documented result is completion of the stand-alone dump followed by disabled wait. * +0 Availability not awarded: the system is already executing its crash-dump shutdown path, and the commit explicitly states that the fix does not change the final behavior when no re-IPL parameter block exists. * +0 B5-R not applicable: there is no heap OOB write, retry accumulation, or later consumption of corrupted heap state. * +0 B3-PENDING not applicable: there is no shared-backing write. * +0 Authorization bypass not applicable: no mandatory access-control decision changes from DENY to ALLOW. * No UAF, controlled reclaim, OOB write, arbitrary write, disclosure, repeated lifetime mutation, privilege escalation, or protected-resource impact is established. * No hardware or niche-path penalty was applied because the score is already zero and such a penalty would not add useful discrimination. 3. Reachability analysis The defect is limited to the s390 stand-alone dump and re-IPL path when the machine was booted without an IPL parameter block, including HMC FTP boot or QEMU direct kernel boot. Reaching it requires the relevant boot state, stand-alone dump configuration, and execution of the dump shutdown action. The supplied patch does not expose the complete trigger interface or its permission checks. Host-administrator control is therefore plausible but not sufficiently established for `HostAdminRequired=YES`. Below-host-admin reachability is also not established, so the correct value is `UNKNOWN`. No namespace-scoped trigger, remote path, ordinary-user interface, race, or attacker-controlled retry mechanism is shown. 4. Primitive and severity interpretation The exact primitive is a NULL-derived invalid read in `dump_reipl_run()`. It is not a UAF, heap corruption, active structured-object lifetime violation, or repeated release. The code may fault while reading address zero, but on s390 it may instead read lowcore data and continue. The demonstrated operational consequence is that a zero IPL parameter-block address is stored and the stand-alone dumper enters disabled wait after completing the dump. The commit states that explicitly writing zero after the fix preserves this outcome when no valid re-IPL block exists. Thus the patch primarily removes an unsafe dereference and makes the existing terminal behavior deterministic. There is no leverage beyond a possible fault in an already exceptional crash-dump path. `PrimitiveClass=CLASS_C` is appropriate. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` follow because no unresolved corruption, ownership, authorization, or security-boundary primitive exists. 5. One-sentence report phrase The s390 stand-alone dump path could dereference a NULL re-IPL parameter block, but the demonstrated effect is confined to an exceptional dump shutdown workflow and no memory corruption, authorization bypass, or privilege-escalation primitive is established. 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is a constrained NULL-derived invalid read with no demonstrated security primitive beyond possible failure in an already terminating dump path. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: s390/ipl: Fix NULL deref in dump_reipl without re-IPL parm block [ Upstream Commit: 41647864e62b28388ecccc23a82f0e0a091f4ef2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=41647864e62b28388ecccc23a82f0e0a091f4ef2 Changed files: arch/s390/kernel/ipl.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=41647864e62b28388ecccc23a82f0e0a091f4ef2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98399 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98399 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:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.1 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).