From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99192][LOW] net: bcmgenet: unshare the skb before writing the control block [ Upstream Date: Fri, 30 Oct 2026 12:10:47 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99192 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: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 40c04abcbc34e3afe338f41dae851ecbd72852ac List-Id: CVE: CVE-2026-99192 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: net: bcmgenet: unshare the skb before writing the control block [ Upstream Commit: 40c04abcbc34e3afe338f41dae851ecbd72852ac Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=40c04abcbc34e3afe338f41dae851ecbd72852ac Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99192 Analysis date: Fri, 30 Oct 2026 12:10:47 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A shared skb permits bcmgenet transmit metadata to be overwritten before completion, causing incorrect BQL accounting and a recoverable transmit-queue stall. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99192 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99192 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-2026-99192 LOW https://www.kernelcve.org/list/?q=CVE-2026-99192 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'bcmgenet stores transmit state in the skb control block even though the network stack may resubmit a shared skb while an earlier transmission is still present in the ring. The later transmission can overwrite last_cb and related state, causing earlier completions to miss BQL byte credits and leaving the transmit queue stalled until the watchdog resets the device. For the CVSS the PR:L value is selected because exploitation requires a local packet generation context and access to traffic using the affected interface, while the demonstrated pktgen clone_skb reproducer may require additional administrative setup. The base AC:H reflects the need to overlap reuse of a shared skb with an outstanding ring entry. No OOB access, UAF, information disclosure, or arbitrary write is demonstrated because the overwrite remains inside the valid skb control block. The established impact is availability loss affecting the transmit queue, with sustained interface disruption considered only in the paranoid score. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation 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 LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 2.3 and ActionableScore 1 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 LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE REMOTE LEAK NETWORK SKB LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 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 base score: 2. * Conservative score: 2; no floor or cap applied. * Raw paranoid score: 2. * Paranoid score: 2; sustained disruption is the same device-local availability effect and is not counted twice. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 weak/indirect state corruption: a later transmission writes `first_cb`, `last_cb`, and `bytes_sent` into a shared skb control block, overwriting state belonging to an earlier outstanding transmission. * +1 availability impact: completion consumes the overwritten `last_cb`/accounting state, misses BQL credits, and stalls the transmit queue until watchdog recovery. * No crash point: no kernel panic, fatal fault, or host-wide DoS is shown. * No strong corruption point: the writes remain within the valid skb control block; no OOB write, UAF, arbitrary target, controlled payload, callback corruption, or reclaim is shown. * No privilege penalty: pktgen configuration may require administrative rights, but the complete trigger privilege is not established. * No race penalty: overlap is required, but the evidence does not establish a narrow or materially uncontrollable race. * No C/I points: no disclosure or unauthorized modification of protected state is demonstrated. 3. Reachability analysis The demonstrated reproducer uses pktgen `clone_skb`, but its exact host capability requirements and whether ordinary traffic can independently force the same shared-skb resubmission are not established. The evidence does not resolve whether all required operations work with namespace-scoped privileges, delegated interface access, or only host administration. No special timing penalty is justified because repeated cloned transmission deliberately maintains overlap. 4. Primitive and severity reading The exact write is an in-bounds overwrite of active per-transmission skb control-block state. The later privileged kernel consumer is the bcmgenet transmit-completion path, which uses that state for skb completion and BQL crediting. The demonstrated result is device/queue-local availability loss with watchdog recovery. No credible guest-to-host, namespace-to-host, or delegated-interface security boundary is grounded in the supplied evidence. Therefore the V33 active-state trust-boundary candidate rule does not apply. This is CLASS_C rather than CLASS_B/A because only constrained invalid-state consumption and queue stalling are shown. Auto-downgrade remains allowed. 5. One-sentence report phrase A shared skb permits bcmgenet transmit metadata to be overwritten before completion, causing incorrect BQL accounting and a recoverable transmit-queue stall. 6. Manual review advice NO MANUAL CHECK NEEDED The patch establishes a bounded state-sharing bug with device-local availability impact and no unresolved material corruption or trust-boundary primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: bcmgenet: unshare the skb before writing the control block [ Upstream Commit: 40c04abcbc34e3afe338f41dae851ecbd72852ac Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=40c04abcbc34e3afe338f41dae851ecbd72852ac Changed files: drivers/net/ethernet/broadcom/genet/bcmgenet.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=40c04abcbc34e3afe338f41dae851ecbd72852ac ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99192 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99192 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:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: 2 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).