From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64048][MODERATE 7.0] net/smc: reject CHID-0 ACCEPT that matches an empty ism_dev slot [ Upstream Date: Sun, 19 Jul 2026 20:09:36 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64048 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: 6927cacf2b10d4fa80c1a2d407512ef9397c59c6 List-Id: CVE: CVE-2026-64048 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: net/smc: reject CHID-0 ACCEPT that matches an empty ism_dev slot [ Upstream Commit: 6927cacf2b10d4fa80c1a2d407512ef9397c59c6 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6927cacf2b10d4fa80c1a2d407512ef9397c59c6 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64048 Analysis date: Sun, 19 Jul 2026 20:09:36 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malicious SMC-Dv2 peer can reply with CHID 0 and cause the client to select an empty ISM device slot, leading to a NULL pointer dereference in `smc_conn_create()` and a network-triggerable kernel crash. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64048 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64048 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-2026-64048 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;*CWE-20;CWE-754;BEST CVSS score: '7.5';DESCR 'A NULL pointer dereference in the SMC-D client CHID selection path can occur because CHID 0 from a peer can match the empty reserved slot 0 when no SMC-Dv1 device is selected. A malicious SMC peer can reply to an SMC-Dv2 only proposal with CHID 0, causing the client to select a NULL ISM device and later dereference lgr_lock during connection setup. For the CVSS the PR:N is used because the attacker only needs to control the peer endpoint or traffic seen by the SMC client, not a local account on the victim. The issue is network reachable in deployments where SMC-D or SMC-Dv2 negotiation is enabled and a client connects to an attacker controlled peer. Impact is denial of service only because the primitive shown by the code is a NULL pointer dereference, not UAF or controllable memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES KASAN NULLPTR HARDWARE KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum** ## 2. Signal breakdown Conservative signals: * Remote reachable / network-triggerable: +2. A malicious SMC peer can send an ACCEPT with CHID 0 during SMC-Dv2 negotiation. * Reliable kernel crash / strong DoS: +1. The described path reaches `ism_dev[0]->lgr_lock` with `ism_dev[0] == NULL`, causing a NULL pointer dereference. * Availability impact realistic: +1. The effect is a host kernel crash during connection setup, not merely a warning. * Practical exploit chain demonstrated or strongly implied: +1. The commit describes the exact malicious peer response and call path to the fault. * Rare AND difficult-to-reach subsystem/configuration: -1. Practical exposure depends on SMC-D/SMC-Dv2 support and relevant deployment conditions. Paranoid difference: * In environments where SMC-Dv2 is enabled and used, the rare-configuration penalty may be removed, giving score 5. Not counted: * Generic memory corruption: +0. The demonstrated primitive is NULL pointer dereference, not UAF, OOB write, type confusion, or controllable overwrite. * Privilege escalation plausible: +0. No reclaim, write primitive, callback control, or object replacement is shown. * Confidentiality / integrity impact: +0. The patch supports DoS only. ## 3. Reachability analysis The bug can be triggered by a malicious peer participating in SMC-Dv2 negotiation with an affected client. The attacker does not need a local account on the victim if they can act as the peer endpoint or otherwise influence the negotiation traffic. Namespaces and containers are not the main factor here because the vulnerable action is on the client connection path. Realistic exploitation requires that SMC-D/SMC-Dv2 is available and negotiated, so exposure is narrower than common TCP/IP packet processing but still network-reachable in affected deployments. Call-site confidence: high. The commit provides the direct caller chain from `smc_v2_determine_accepted_chid()` to `smc_conn_create()` and the concrete NULL dereference site. ## 4. Severity interpretation This behaves like an actionable Moderate network-reachable DoS, not an Important-class memory corruption issue. The theoretical impact is limited by the primitive: selecting an empty slot causes a NULL pointer dereference at a fixed low offset. There is no evidence of attacker-controlled memory corruption, UAF reuse, information disclosure, or privilege escalation. However, because the crash is remotely triggerable by a malicious peer in affected SMC-Dv2 deployments, it should not be auto-closed as an ordinary low-priority correctness fix. ## 5. One-sentence report phrase A malicious SMC-Dv2 peer can reply with CHID 0 and cause the client to select an empty ISM device slot, leading to a NULL pointer dereference in `smc_conn_create()` and a network-triggerable kernel crash. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: network-reachable kernel crash with a clear malicious peer trigger, even though the demonstrated primitive is DoS-only and does not support LPE or memory corruption escalation. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net/smc: reject CHID-0 ACCEPT that matches an empty ism_dev slot [ Upstream Commit: 6927cacf2b10d4fa80c1a2d407512ef9397c59c6 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6927cacf2b10d4fa80c1a2d407512ef9397c59c6 Changed files: net/smc/smc_core.c net/smc/af_smc.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=6927cacf2b10d4fa80c1a2d407512ef9397c59c6 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64048 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64048 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: Not available The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 7.5 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).