From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90146][MODERATE 7.0] bpf, xdp: move offload check into dev_xdp_install() [ Upstream Date: Thu, 17 Sep 2026 19:09:51 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90146 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: ea7b35dcc9430293b861bc7bad0c546f193c85f9 List-Id: CVE: CVE-2026-90146 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: bpf, xdp: move offload check into dev_xdp_install() [ Upstream Commit: ea7b35dcc9430293b861bc7bad0c546f193c85f9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ea7b35dcc9430293b861bc7bad0c546f193c85f9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90146 Analysis date: Thu, 17 Sep 2026 19:09:51 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90146 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90146 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-90146 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90146 CHECK WITH IMPACT FROM ORIG NN LOW 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-693;*CWE-20;CWE-284;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'An XDP link update validation bypass exists because bpf_xdp_link_update calls dev_xdp_install directly and did not run the compatibility checks kept in dev_xdp_attach. A user could create an XDP link with a normal program and then replace it with an offloaded or device-bound program through BPF_LINK_UPDATE, causing a program that should be restricted to hardware offload or a specific device to be placed on the software XDP path. This is not directly network reachable by packet traffic alone, but packets may exercise the bad attachment after a local control plane update. For the CVSS the PR:L is used for the paranoid score because exploitation can be performed by a local user or service that already has delegated BPF/XDP update capability, such as CAP_BPF and CAP_NET_ADMIN or an equivalent capability in the target environment. Impact is mainly denial of service or validation policy bypass. The patch context does not show a concrete arbitrary write or information leak primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate (with actual score 5) YES REMOTE BPF SKB HARDWARE LINUS KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 4 * Conservative score: 4. No floor or cap applied. * Raw paranoid score: 5 * Paranoid score: 5. No floor or cap applied. * Final recommended bucket: **Actionable Moderate**:: 2. Signal breakdown * +2: Concrete validation and policy bypass. `BPF_LINK_UPDATE` reached `dev_xdp_install()` directly and skipped checks that would otherwise reject offloaded, device-bound, wrong-device, generic-mode-incompatible, `DEVMAP`, and `CPUMAP` XDP programs. * +1: Externally meaningful BPF/XDP attach-state impact. The bypass can place a program into a software XDP path where the normal attach model says it must not run. * +1: BPF/XDP packet-processing relevance. The bad state is created through control-plane update, but packets can later exercise the incorrectly installed program on the data path. * Paranoid +1: The wrong-mode attachment creates an unresolved BPF/XDP runtime semantic mismatch between offload/device-bound assumptions and software execution. This is not scored as memory corruption, but it is enough to avoid automatic closure. Non-awarded signals: * Real UAF not awarded. No stale pointer, freed object, double release, or lifetime violation is shown. * Controlled reclaim not demonstrated. * Arbitrary write not demonstrated. * Confidentiality and integrity not awarded because the patch does not establish a disclosure path, protected-object write, or concrete kernel memory corruption primitive. * Reliable kernel crash not conservatively awarded because the commit establishes invalid attachment state, not a specific observed panic. * Remote reachability not awarded. Packet traffic alone does not create the bad attachment. * Local unprivileged trigger not awarded because BPF/XDP load, link creation, link update, and netdevice control privileges are not resolved as ordinary-user reachable. * Host-admin penalty not applied because host-admin-equivalent privilege is not positively established from the supplied evidence. * Namespace-scoped privilege not awarded because complete BPF load, XDP attach, link update, and target netdevice control are not proven to be namespace-scoped. 3. Reachability analysis The trigger is local control-plane manipulation of BPF/XDP state. An attacker must create an XDP link with a normal program and then use `BPF_LINK_UPDATE` to replace it with an offloaded or device-bound program that normal attach checks would reject. This is not directly network-triggerable. Network packets may exercise the invalid state after the local update, but packets alone do not perform the vulnerable operation. For BPF/XDP, the complete privilege chain is unresolved. Program loading and XDP attachment commonly require `CAP_BPF`, `CAP_NET_ADMIN`, `CAP_SYS_ADMIN`, ownership of relevant BPF objects, or an equivalent delegated service context. The supplied patch does not prove that an ordinary local user can perform the full sequence. Namespace scope is also unresolved. Some netdevice operations may be namespace-aware, but the complete chain including BPF program creation, link creation, link update, and target device control is not proven to work entirely inside attacker-created namespaces. No special hardware is strictly required for the generic bypass pattern, although offloaded or device-bound program cases may depend on device/offload support. There is no race or timing dependency. 4. Primitive and severity interpretation The exact primitive is a BPF/XDP validation bypass. A program that should be rejected for the selected XDP mode or device can be installed through the `BPF_LINK_UPDATE` path because checks were placed in `dev_xdp_attach()` while `bpf_xdp_link_update()` called `dev_xdp_install()` directly. This is not an active-object UAF and not fixed stale storage. There is no cleanup/destructor stale use and no concrete repeated release/refcount operation. Primitive class is `CLASS_C`: invalid kernel control-plane state with possible DoS or policy-bypass consequences, but without an independently established memory-corruption primitive. Demonstrated consequence is incorrect acceptance of unsupported XDP program combinations. Speculative consequence is a stronger runtime failure if the wrongly installed program violates assumptions of the software XDP path. The evidence does not establish arbitrary read/write, privilege escalation, or information disclosure. ImportantCandidate is `NO` because the patch does not establish Class A corruption, LPE, protected resource access, or a strong Class B lifetime primitive. AutoDowngradeAllowed is `NO` because this is a meaningful BPF/XDP validation bypass affecting packet-processing attachment semantics, so automatic closure as an ordinary low-impact issue could miss environment-specific impact. Likely operational severity is Actionable Moderate. 5. One-sentence report phrase A BPF/XDP link update validation bypass allowed `BPF_LINK_UPDATE` to install offloaded or device-bound XDP programs into an unsupported software path, requiring local BPF/XDP update capability and potentially causing denial of service or policy bypass when the invalid attachment is exercised. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: no concrete UAF or arbitrary write is shown, but this is a BPF/XDP validation bypass on a packet-processing attachment path with unresolved environment-dependent impact and unresolved privilege scope. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf, xdp: move offload check into dev_xdp_install() [ Upstream Commit: ea7b35dcc9430293b861bc7bad0c546f193c85f9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ea7b35dcc9430293b861bc7bad0c546f193c85f9 Changed files: net/core/dev.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=ea7b35dcc9430293b861bc7bad0c546f193c85f9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90146 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90146 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:L/PR:H/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: 4 Paranoid ActionableScore: 5 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).