From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98631][MODERATE REGULAR] xsk: Use a 32-bit compare in xsk_map_gen_lookup [ Upstream Date: Sat, 24 Oct 2026 12:24:23 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98631 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: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: c6d5c582d55a8f229d75e98d62eaa065b0deb18d List-Id: CVE: CVE-2026-98631 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: xsk: Use a 32-bit compare in xsk_map_gen_lookup [ Upstream Commit: c6d5c582d55a8f229d75e98d62eaa065b0deb18d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c6d5c582d55a8f229d75e98d62eaa065b0deb18d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98631 Analysis date: Sat, 24 Oct 2026 12:24:23 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A signed-width error in generated XSKMAP lookup code permits an extreme-size map index to read beyond the pointer array and potentially use adjacent data as an `xsk_sock` pointer. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98631 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98631 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98631 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98631 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-125;CWE-194;CWE-681;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A generated XSKMAP lookup used a 64 bit BPF immediate comparison for a 32 bit key. When max_entries is at least 0x80000000, sign extension makes the comparison threshold larger than every zero extended key, allowing an out of range index to reach an out of bounds pointer load from xsk_map. The confirmed primitive is an out of bounds read of a value later treated as an xsk_sock pointer, with a plausible kernel crash if the invalid pointer is used. Limited confidentiality or integrity impact remains possible but unproven because the loaded value may cross a kernel object boundary, while no controlled write or direct information disclosure is demonstrated. For the CVSS the PR:L value reflects that reliable triggering requires a local user or service context able to create a very large XSKMAP and load or use the relevant BPF program. AC:H reflects the extreme map size and substantial memory requirement. Remote packet influence alone does not establish remote reachability. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.8 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore 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 INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.1 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE OOB BPF SIMPLEFIX IMPROVEONLY LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=REQUIRED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 2. * Conservative score: 2; no floor or cap applied. * Raw paranoid score: 3. * Paranoid score: 3; no floor or cap applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +1 weak/indirect corruption candidate: the signed 64-bit immediate comparison can admit a zero-extended out-of-range index, causing a confirmed read beyond `xsk_map[]`. * +1 plausible kernel crash: the loaded out-of-bounds word is treated as an `xsk_sock` pointer, so later use can fault. * Paranoid +1 unsafe active-object selection: cross-object bytes may become a kernel object pointer consumed by generated lookup users. The exact dereference and any useful non-crash effect are not shown. * No privilege penalty: host-admin-equivalent privilege is not positively established. * No confidentiality, integrity, disclosure, write, controlled target, reclaim, or LPE points. * No extra availability point; it would duplicate the same possible crash. * NEW52/B5-R does not apply: there is no retry-accumulated OOB write. * NEW53/B3-PENDING and NEW54/B4-PENDING do not apply. 3. Reachability analysis Triggering requires creation of an XSKMAP with `max_entries >= 0x80000000` and execution of the generated BPF lookup. This implies extreme allocation pressure and likely configuration or BPF privilege constraints, but the supplied patch does not establish the complete capability checks, namespace scope, or below-host-admin path. Remote packets alone do not establish reachability. No timing race or special hardware is required. 4. Primitive and severity reading The proven primitive is a heap/slab-adjacent OOB pointer read caused by a 64-bit sign-extension mismatch. It is not a UAF or write. The downstream value is interpreted as an active `xsk_sock` pointer, but the supplied code does not show a controlled dereference, disclosure, callback, or state mutation. This supports CLASS_C and plausible DoS, not an Important-grade corruption primitive. ImportantCandidate is therefore NO; downgrade remains allowed after the required reachability and consumer review. 5. One-sentence report phrase A signed-width error in generated XSKMAP lookup code permits an extreme-size map index to read beyond the pointer array and potentially use adjacent data as an `xsk_sock` pointer. 6. Manual review advice MANUAL CHECK REQUIRED Confirm BPF/XSK privilege scope, feasibility of the very large allocation, and the first downstream consumer of the invalid pointer. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xsk: Use a 32-bit compare in xsk_map_gen_lookup [ Upstream Commit: c6d5c582d55a8f229d75e98d62eaa065b0deb18d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c6d5c582d55a8f229d75e98d62eaa065b0deb18d Changed files: net/xdp/xskmap.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=c6d5c582d55a8f229d75e98d62eaa065b0deb18d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98631 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98631 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:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 2 Paranoid ActionableScore: 3 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).