From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98803][MODERATE 7.0] net: stmmac: fix rx Scatter-Gather support [ Upstream Date: Sat, 24 Oct 2026 03:58:04 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98803 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 4 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 358d5ac5a5d57ce21c3814c4e3e8f3fbcb7304b4 List-Id: CVE: CVE-2026-98803 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: net: stmmac: fix rx Scatter-Gather support [ Upstream Commit: 358d5ac5a5d57ce21c3814c4e3e8f3fbcb7304b4 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=358d5ac5a5d57ce21c3814c4e3e8f3fbcb7304b4 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98803 Analysis date: Sat, 24 Oct 2026 03:58:04 -0400 ActionableScore: 4 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: Oversized received frames can make affected stmmac hardware DMA through an unbacked buffer2 address, causing a confirmed IOMMU fault and possible RX disruption, while non-IOMMU memory corruption remains unproven. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98803 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98803 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 7.0 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-2026-98803 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98803 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-824;*CWE-20;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '8.8';DESCR 'stmmac could program RX buffer2 with an invalid DMA address when split header mode was disabled. An accepted frame larger than dma_buf_sz can overflow buffer1 and make the device write the remaining attacker controlled frame data through buffer2. On IOMMU systems this produces an SMMU translation fault and can disrupt RX processing. On systems lacking IOMMU protection DMA address zero may refer to low physical memory, creating a plausible memory corruption primitive with possible integrity and availability impact. For the CVSS the PR:N value is selected because an attacker only needs adjacent network reachability and does not need a local user context or privileges on the target. AV:A is used because reliable triggering normally requires direct Layer 2 access and an oversized frame accepted by the target MAC. The required stmmac hardware, frame size, MTU configuration, dma_buf_sz relation, and IOMMU behavior limit practical exposure. The patch explicitly does not protect AF_XDP zero copy RX, where oversized frames may still reach buffer2 at DMA address zero. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 8.8 and the production ActionableScore returned 4 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 MODERATE_KPANIC to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because KP specialist did not establish a qualifying panic. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP. The independent weaker Aegis shadow evaluated CVSS unavailable and ActionableScore 4 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE REMOTE OOB NETWORK SKB DMAorINTERRUPT HARDWARE LINUS KPANIC MEMORY PACKET KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 4 * Conservative score: 4; no floor or cap applied. * Raw paranoid score: 4 * Paranoid score: 4; non-IOMMU physical-memory corruption remains plausible but unproven and receives no extra point. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +2 — Adjacent network reachability: an oversized frame accepted by the MAC directly triggers buffer2 DMA without attacker host privileges. * +1 — Weak/indirect corruption candidate: the descriptor supplies DMA address zero without a valid secondary-buffer mapping. * +1 — Device/network DoS: the confirmed SMMU translation fault can disrupt RX processing. * No hardware/configuration penalty: stmmac hardware and jumbo-frame configuration constrain exposure, but rarity and difficult reachability are not established. * No heap/slab OOB-write score: the shown IOMMU case blocks the DMA write and faults; no kernel heap target is identified. * No strong DMA-corruption score: writes to low physical memory without an IOMMU are plausible, not demonstrated. * No C/I, arbitrary-write, host-crash, or LPE points. * NEW52/B5-R does not apply: there is no retry-accumulated index and no confirmed heap OOB write. * NEW53/B3-PENDING and B4 authorization profiles do not apply. 3. Reachability analysis The assessed attacker is an adjacent network sender requiring no target UID or capability. The target must use affected stmmac hardware and accept a frame larger than `dma_buf_sz`, normally through jumbo-frame configuration; this is prior administrative configuration, not attacker privilege. No namespace capability is involved. Trigger timing is deterministic rather than a race. AF_XDP zero-copy remains separately unfixed, but does not strengthen the patched path’s proven impact. 4. Primitive and severity reading The exact shown primitive is attacker-influenced frame data causing hardware to attempt DMA through an invalid buffer2 address. On the evidenced IOMMU platform, translation enforcement prevents the write and reports a fault, supporting CLASS_C invalid-state/DoS behavior. A fixed-address DMA overwrite of low physical memory on non-IOMMU systems is a credible review question, but neither a valid target nor actual corruption is shown. Therefore this is not an Important candidate and may be downgraded after platform review. 5. One-sentence report phrase Oversized received frames can make affected stmmac hardware DMA through an unbacked buffer2 address, causing a confirmed IOMMU fault and possible RX disruption, while non-IOMMU memory corruption remains unproven. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm whether affected product platforms lack DMA translation and whether DMA address zero can target host memory. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: stmmac: fix rx Scatter-Gather support [ Upstream Commit: 358d5ac5a5d57ce21c3814c4e3e8f3fbcb7304b4 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=358d5ac5a5d57ce21c3814c4e3e8f3fbcb7304b4 Changed files: drivers/net/ethernet/stmicro/stmmac/stmmac_main.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=358d5ac5a5d57ce21c3814c4e3e8f3fbcb7304b4 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98803 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98803 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:L/PR:N/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 8.8 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: unknown Paranoid ActionableScore: 4 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: YES Published priority for this report (same as in Subject): MODERATE 7.0 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).