From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80733][LOW] net: remove WARN_ON_ONCE() from sk_mc_loop() [ Upstream Date: Thu, 03 Sep 2026 05:25:40 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80733 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: 1 X-AL-KERNEL-Commit: 97133c4d42654578fab95abe47359ebe784dde18 List-Id: CVE: CVE-2026-80733 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: net: remove WARN_ON_ONCE() from sk_mc_loop() [ Upstream Commit: 97133c4d42654578fab95abe47359ebe784dde18 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=97133c4d42654578fab95abe47359ebe784dde18 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80733 Analysis date: Thu, 03 Sep 2026 05:25:40 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A local process using non-INET sockets such as AF_PACKET over virtual networking paths can trigger a reachable WARN_ON_ONCE in sk_mc_loop, which is normally limited to a kernel warning but may become a DoS on systems configured with panic_on_warn. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80733 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80733 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-2026-80733 LOW https://www.kernelcve.org/list/?q=CVE-2026-80733 CHECK WITH IMPACT FROM ORIG NN MODERATE 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-617;CWE-703;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'sk_mc_loop can be reached with sockets that are not AF_INET or AF_INET6, for example AF_PACKET sockets sending traffic over virtual devices such as VRF or ipvlan. In that case the function falls through the address family switch and triggers WARN_ON_ONCE(1), even though non INET sockets do not support IP_MULTICAST_LOOP or IPV6_MULTICAST_LOOP and should simply use the default loopback behavior. For the CVSS the PR:L is selected because a local process with packet socket capability or similar delegated network capability is typically needed to reach this path. The issue is not directly network reachable because it is triggered through local socket use rather than by receiving remote packets. Impact is denial of service at most. On normal systems this is mainly a kernel warning or log noise, while systems configured with panic_on_warn may convert the warning into a kernel crash.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES REMOTE DANGER HARDWARE IPV6 SYZBOT PACKET DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Conservative signals: * Reachable WARN_ON condition: +1 `sk_mc_loop()` can be reached with non `AF_INET` and non `AF_INET6` sockets and can trigger `WARN_ON_ONCE(1)`. * No memory corruption: +0 The patch only removes a warning. There is no UAF, OOB access, stale pointer use, double free, type confusion, or write primitive. * No direct remote reachability: +0 The path is triggered through local socket usage, not by receiving network packets. * No strong DoS in default configuration: +0 On normal systems this is mainly a kernel warning. It becomes a crash mainly if `panic_on_warn` is enabled. Paranoid additional signal: * Potential panic_on_warn crash impact: +1 If the system is configured with `panic_on_warn`, the reachable warning may cause a kernel panic. Not awarded: * Remote reachable: +0 * Generic memory corruption: +0 * Real lifetime corruption: +0 * Privilege escalation plausible: +0 * Confidentiality impact: +0 * Integrity impact: +0 * Common packet-processing path bonus: +0 This is in `net/core`, but the trigger is a specific local socket path involving non-INET sockets over virtual devices, not a common remote packet receive path. ## 3. Reachability analysis The issue is locally triggerable by a process able to create or use relevant non-INET sockets such as `AF_PACKET` and send through paths involving virtual devices like VRF or ipvlan. In typical deployments this requires `CAP_NET_RAW` and possibly pre-existing network configuration or `CAP_NET_ADMIN` to create the relevant virtual device setup. User namespaces or containers may reduce the practical privilege barrier if packet sockets and delegated networking are available, but this still does not make the bug remotely network-triggerable. The affected code is present in a common networking helper, but the problematic path is not a default remote exposure path. ## 4. Severity interpretation This behaves like a low-end Moderate or Low-like issue, not an Important-class vulnerability. The realistic impact is a reachable kernel warning and possible log noise. A stronger availability impact exists mainly on systems that intentionally panic on warnings. There is no evidence of memory corruption, object lifetime misuse, data disclosure, integrity impact, or privilege escalation. The paranoid score is therefore raised only slightly for `panic_on_warn`, not into Actionable Moderate territory. ## 5. One-sentence report phrase A local process using non-INET sockets such as AF_PACKET over virtual networking paths can trigger a reachable WARN_ON_ONCE in sk_mc_loop, which is normally limited to a kernel warning but may become a DoS on systems configured with panic_on_warn. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed or handled in deferred mode unless the evaluated product enables `panic_on_warn` in production or exposes packet-socket based networking capabilities to untrusted users or containers. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: remove WARN_ON_ONCE() from sk_mc_loop() [ Upstream Commit: 97133c4d42654578fab95abe47359ebe784dde18 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=97133c4d42654578fab95abe47359ebe784dde18 Changed files: net/core/sock.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=97133c4d42654578fab95abe47359ebe784dde18 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80733 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80733 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: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: 1 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).