From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2025-21960][MODERATE REGULAR] eth: bnxt: do not update checksum in bnxt_xdp_build_skb() [ Upstream Date: Mon, 12 Oct 2026 21:51:48 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2025-21960 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: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: e8e3e03d69f2420eaa578199a65d281c58867105 List-Id: CVE: CVE-2025-21960 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: eth: bnxt: do not update checksum in bnxt_xdp_build_skb() [ Upstream Commit: e8e3e03d69f2420eaa578199a65d281c58867105 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8e3e03d69f2420eaa578199a65d281c58867105 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-21960 Analysis date: Mon, 12 Oct 2026 21:51:48 -0400 ActionableScore: 1 ActionableScore lower bound: 0 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-2025-21960 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-21960 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2025-21960 MODERATE https://www.kernelcve.org/list/?q=CVE-2025-21960 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF TEMP_DISTANCE_MERGE=MODERATE_KPANIC->MODERATE;AEGIS=LOW;GAP=2 (independent Legacy and Aegis differ; FINAL: MODERATE, Aegis: LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-617;CWE-682;CWE-754;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'A logic error in the bnxt XDP multi buffer pass path causes the checksum state of an skb to be updated twice. bnxt_xdp_build_skb can set ip_summed to CHECKSUM_UNNECESSARY before bnxt_rx_pkt performs its normal checksum handling, causing skb_checksum_none_assert to emit a kernel warning because CHECKSUM_NONE was expected. No UAF, out of bounds access, information disclosure, or write primitive is evident from the affected path. The normal impact is a kernel warning and reduced availability at most. A system configured with panic_on_warn may convert the warning into a kernel panic and complete denial of service. For the CVSS the PR:N value is selected because network traffic can reach the receive path without a local user account after an administrator has attached the required XDP multi buffer program. AC:H reflects the nondefault requirement for a supported bnxt device, checksum offload, an XDP multi buffer program, and an XDP_PASS result. The issue can be network reachable, although practical exposure depends on whether suitable traffic can reach the affected interface.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE REMOTE NETWORK SKB HARDWARE LINUS MEMORY LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 TEMP_DISTANCE_MERGE - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 0 * Conservative score: 0 * Raw paranoid score: 1 * Paranoid score: 1 * No floor or cap applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * Conservative +0: The demonstrated consequence is `skb_checksum_none_assert()` emitting `WARN_ON`, which does not establish a fatal consequence. * Paranoid +1: A host configured with `panic_on_warn` can convert the reachable warning into a kernel panic and host DoS. * Remote reachable +2 not awarded: packet input can exercise the configured path, but prior privileged loading and attachment of an XDP multi-buffer program is a material prerequisite. * Memory-corruption points not awarded: no UAF, OOB access, overwrite, stale object, refcount corruption, or shared-backing write is established. * Availability was not counted twice. The paranoid panic contributes one DoS point only. * No confidentiality, integrity, authorization-bypass, or privilege-escalation signal exists. * B5-R does not apply because there is no heap OOB write or retry-accumulated offset. * B3-PENDING does not apply because there is no write to shared or file-backed storage. * B4-PENDING does not apply because no DENY-to-ALLOW authorization decision is changed. 3. Reachability analysis The receive path is exercised by network packets after a supported Broadcom bnxt device has an XDP multi-buffer program attached and that program returns `XDP_PASS`. A network sender can then reach the warning without local credentials, so effective host-admin privilege is not required for the packet-trigger stage. The necessary XDP load and attachment are prior privileged configuration. Their complete user-namespace and capability scope is not established, so `NamespaceScopedPrivilege=UNKNOWN`. The physical bnxt adapter and enabled checksum offload are prerequisites, but no hardware penalty is applied merely because this is driver-specific. There is no timing race. 4. Primitive and severity interpretation The exact defect is duplicate checksum-state handling. `bnxt_xdp_build_skb()` sets `skb->ip_summed` before `bnxt_rx_pkt()` performs the normal checksum update, violating the assertion that the state is still `CHECKSUM_NONE`. This is invalid-state and reachable-assertion behavior, classified as CLASS_C. It is not a lifetime violation, memory overwrite, active-state retirement bypass, or authorization flaw. The demonstrated result is a warning and kernel taint. Kernel panic is conditional on `panic_on_warn`. No useful primitive remains after excluding the warning or conditional panic. Therefore `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES`. 5. One-sentence report phrase A duplicate checksum-state update in the bnxt XDP multi-buffer pass path triggers a kernel warning, with host denial of service possible only when warnings are configured to panic. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch establishes a WARN-only logic error without memory corruption, lifetime corruption, authorization bypass, or an independent integrity primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: eth: bnxt: do not update checksum in bnxt_xdp_build_skb() [ Upstream Commit: e8e3e03d69f2420eaa578199a65d281c58867105 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8e3e03d69f2420eaa578199a65d281c58867105 Changed files: include/linux/skbuff.h drivers/net/ethernet/broadcom/bnxt/bnxt.c drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h 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=e8e3e03d69f2420eaa578199a65d281c58867105 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2025-21960 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-21960 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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.9 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: 0 Paranoid ActionableScore: 1 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).