From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99081][MODERATE REGULAR] bnxt_en: fix DMA mapping length for padded small packets [ Upstream Date: Mon, 26 Oct 2026 14:49:09 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99081 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: cf8530a25ae92c4493e2f22981ecb46f0b66f4c8 List-Id: CVE: CVE-2026-99081 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: bnxt_en: fix DMA mapping length for padded small packets [ Upstream Commit: cf8530a25ae92c4493e2f22981ecb46f0b66f4c8 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cf8530a25ae92c4493e2f22981ecb46f0b66f4c8 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99081 Analysis date: Mon, 26 Oct 2026 14:49:09 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A short padded bnxt packet can make the NIC read beyond its DMA mapping, causing an IOMMU fault and transmit-queue timeout without a demonstrated memory write or disclosure. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99081 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99081 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-2026-99081 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99081 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=MODERATE RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-125;CWE-131;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'bnxt_en mapped only the original head length of a small packet even after padding it to the minimum transmit size. The NIC descriptor then requested a longer DMA read than the DMA mapping covered, which can cross an IOMMU page boundary and cause a DMA fault followed by firmware errors and a TX queue timeout. For the CVSS the PR:N value reflects that an adjacent network peer may be able to induce short outgoing responses without an authenticated local account, although reliable placement of skb data near a page boundary is not demonstrated. AC:H reflects the required packet size, affected bnxt_en hardware, IOMMU behavior, and unfavorable page boundary placement. The demonstrated primitive is an overread beyond the DMA mapped length rather than beyond the allocated padded skb, so confidentiality and integrity impact are not supported. Availability impact is normally limited to the affected transmit path, while repeated faults could potentially stall the interface. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.3 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 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 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4. The independent weaker Aegis shadow evaluated CVSS 1.6 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE REMOTE WRITE OOB DANGER RACE NETWORK SKB DMAorINTERRUPT HARDWARE MEMORY PACKET DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED 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; adds limited adjacent-network influence, not full remote reachability. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +1 memory-layout invariant: the descriptor requests `len + pad` while only the original `len` is DMA-mapped; the fix makes skb length, head length, DMA mapping, and descriptor length consistent. * +1 availability: the demonstrated IOMMU fault causes firmware errors and a TX queue timeout, plausibly disrupting the affected interface. * Paranoid +1 adjacent-network influence: a peer may induce small outgoing packets such as ARP responses, but control of skb page-boundary placement and the complete trigger is not demonstrated. * No kernel OOB write: this is a device DMA read beyond the mapped extent, apparently still within the padded skb allocation. * No confidentiality: no path returns the extra bytes to an attacker. * No host-wide crash, arbitrary write, UAF, shared-backing modification, or protected-state corruption is shown. * B5-R does not apply: there is no write, retry-accumulated index, or later consumption of corrupted structured state. * B3-PENDING and B4-PENDING do not apply: there is neither a shared-backing write nor an authorization decision. 3. Reachability analysis The vulnerable transmit path is exercised on affected bnxt hardware when a short packet is transmitted and its data lies close enough to an IOMMU page boundary. An adjacent peer may induce a short response, but reliable packet generation and placement are unproven. No local privilege, namespace capability, or UID requirement is established, so host-admin and namespace scope remain unknown. A BCM57412-class NIC and relevant IOMMU behavior are material prerequisites; no timing race is shown. 4. Primitive and severity reading The exact defect is a DMA mapping-length/descriptor-length mismatch causing a bounded device read beyond the mapped region. It produces an IOMMU fault and device transmit-path disruption, not a demonstrated kernel-memory read disclosure or write. This is CLASS_C availability behavior. ImportantCandidate is NO because no material corruption or trust-boundary primitive survives exclusion of the device fault. Auto-downgrade is allowed, though trigger reliability and network exposure merit review. 5. One-sentence report phrase A short padded bnxt packet can make the NIC read beyond its DMA mapping, causing an IOMMU fault and transmit-queue timeout without a demonstrated memory write or disclosure. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm whether an unauthenticated adjacent peer can reliably induce the affected packet layout and whether recovery limits impact to the interface. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bnxt_en: fix DMA mapping length for padded small packets [ Upstream Commit: cf8530a25ae92c4493e2f22981ecb46f0b66f4c8 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cf8530a25ae92c4493e2f22981ecb46f0b66f4c8 Changed files: drivers/net/ethernet/broadcom/bnxt/bnxt.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=cf8530a25ae92c4493e2f22981ecb46f0b66f4c8 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99081 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99081 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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.3 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).