From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64190][MODERATE REGULAR] net: team: fix NULL pointer dereference in team_xmit during mode change [ Upstream Date: Mon, 20 Jul 2026 13:15:00 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64190 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: 4 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 03e9405c518c4d61f28079492f252d6d4e2bac5c List-Id: CVE: CVE-2026-64190 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: net: team: fix NULL pointer dereference in team_xmit during mode change [ Upstream Commit: 03e9405c518c4d61f28079492f252d6d4e2bac5c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=03e9405c518c4d61f28079492f252d6d4e2bac5c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64190 Analysis date: Mon, 20 Jul 2026 13:15:00 -0400 ActionableScore: 4 ActionableScore lower bound: 2 Actionable bucket: Borderline. Manual review recommended Manual review required: YES Summary: A race in the Linux team driver during mode changes can let a concurrent transmit path call a transiently NULL transmit callback, causing a local kernel crash, with CAP_NET_ADMIN normally required but possible lower practical privilege in delegated network namespaces. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64190 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64190 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-64190 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-362;**CWE-476;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in the Linux team network driver can occur during a mode change while team_xmit or team_handle_frame runs on another CPU under RCU. The mode change path previously cleared team ops before restoring dummy handlers, allowing a lockless transmit path to read a NULL transmit callback and call address 0, causing a kernel crash. For the CVSS the PR:L is used for the paranoid score because some environments delegate CAP_NET_ADMIN or expose team device control to container root or service accounts rather than only full host root. The issue is not directly network reachable because the mode change is a local control plane operation, although packet transmission is needed to hit the race window. Impact is at least local denial of service via kernel crash and in worst case may allow limited confidentiality or integrity impact due to stale callback or old mode state exposure, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline. Manual review recommended (with actual score 3) YES KASAN NULLPTR INIT RACE NETWORK SKB KERNEL_PANIC_PLUS_UAF HARDWARE PACKET DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 4 * Final recommended bucket: **Borderline. Manual review recommended** ## 2. Signal breakdown Conservative signals: * Reliable kernel crash / strong DoS: +1 The commit shows a NULL function pointer call from `team_xmit()` leading to an Oops at RIP 0x0. * Real lifetime / RCU concern: +1 The fix adds `synchronize_net()` before `exit_op()` because in-flight RCU readers may still reference old mode state. * Hard or unreliable race / special timing required: -1 Triggering requires a mode change racing with packet transmission on the team device. * Requires CAP_NET_ADMIN in typical deployments: -1 Mode change is a local network control-plane operation requiring CAP_NET_ADMIN, but this may be delegated to containers or service accounts, so I use -1 rather than full -2. Paranoid additional signals: * Weak LPE concern / stale callback state concern: +1 The patch touches function callback dispatch and RCU reader lifetime. There is no demonstrated controllable callback or reclaim primitive, but the stale mode-state aspect deserves manual review. * Common packet-processing path relevance: +1 The crash is reached from transmit-side packet processing via `team_xmit()`, although the configuration path is local and not remotely triggered. No strong memory corruption score is awarded because the demonstrated primitive is a NULL function pointer dereference, not attacker-controlled function pointer corruption, UAF reclaim, OOB write, or arbitrary write. ## 3. Reachability analysis The realistic trigger requires local control over a team device mode change, normally requiring CAP_NET_ADMIN, plus concurrent packet transmission through the team interface. AF_PACKET with forced carrier makes traffic possible even when the old assumption was that no ports meant no packets in flight. This is not directly network reachable because remote packets alone do not change the team mode. Namespace or container setups may reduce the practical privilege barrier if CAP_NET_ADMIN is delegated, so the paranoid interpretation treats this as less than full host-root control. ## 4. Severity interpretation This behaves primarily like a local DoS race in a network driver callback path. The demonstrated impact is a reliable kernel crash when the race is won. Theoretical concern exists around stale callback or old mode state under RCU, but the patch does not show attacker-controlled reuse, arbitrary write, type confusion, or controlled function pointer hijack. Therefore it is not a Strong Important candidate, but it should not be blindly auto-closed without review. ## 5. One-sentence report phrase A race in the Linux team driver during mode changes can let a concurrent transmit path call a transiently NULL transmit callback, causing a local kernel crash, with CAP_NET_ADMIN normally required but possible lower practical privilege in delegated network namespaces. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: this is an RCU/callback race in a network transmit path with a demonstrated crash and some stale state concern, but no proven strong memory corruption or privilege escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: team: fix NULL pointer dereference in team_xmit during mode change [ Upstream Commit: 03e9405c518c4d61f28079492f252d6d4e2bac5c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=03e9405c518c4d61f28079492f252d6d4e2bac5c Changed files: drivers/net/team/team_core.c net/core/dev.c net/packet/af_packet.c net/socket.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=03e9405c518c4d61f28079492f252d6d4e2bac5c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64190 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64190 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:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 2 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: 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).