From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80776][MODERATE REGULAR] futex: Fix race in futex_pivot_pending() during private hash resize [ Upstream Date: Fri, 04 Sep 2026 14:38:09 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80776 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: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 4a7e941ca29a608c6244cbd028d3599ecaef7207 List-Id: CVE: CVE-2026-80776 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: futex: Fix race in futex_pivot_pending() during private hash resize [ Upstream Commit: 4a7e941ca29a608c6244cbd028d3599ecaef7207 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a7e941ca29a608c6244cbd028d3599ecaef7207 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80776 Analysis date: Fri, 04 Sep 2026 14:38:09 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: A race in futex_pivot_pending during private futex hash resize can cause a local process to miss a completed pivot wakeup and remain stuck in uninterruptible sleep, potentially causing a kernel panic when hung task panic is enabled. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80776 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80776 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-2026-80776 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80776 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:N/I:N/A:H';CWE-362;CWE-667;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A race in futex_pivot_pending can make a private futex hash resize task miss the final wakeup and remain blocked in uninterruptible sleep. The bug comes from reading hash_new and hash without serialization, allowing the task to observe a mixed pre pivot and post pivot state and incorrectly decide that the pivot is still pending. For the CVSS the PR:L is used because a local process is required to invoke the private hash resize path and create the futex activity needed for reliable triggering. AC:H is used because the failure depends on a race window between the resize waiter and another futex task completing the pivot. The issue is not network reachable. Impact is denial of service through a stuck D state task and in configurations with hung task panic it can cause a kernel panic.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3) YES WARNONLY RACE INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline, manual review recommended** ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. A local process can reach the private futex hash resize path through the prctl syscall path shown in the trace. * Availability impact realistic: +1. The task can remain stuck in uninterruptible sleep indefinitely. * Broad/default/common subsystem: +1. Futex is core kernel synchronization infrastructure. * Hard or unreliable race / special timing required: -1. The issue depends on observing mixed pre-pivot and post-pivot state across a narrow race window. Paranoid additional interpretation: * Reliable kernel crash / strong DoS: +1. If hung_task_panic or similar policy is enabled, the stuck D-state task can escalate from local task hang to kernel panic. No memory corruption, UAF, OOB write, refcount takeover, stale callback, or privilege escalation primitive is supported by the patch. ## 3. Reachability analysis The bug is locally reachable by a process that can invoke the private futex hash resize path and create concurrent futex activity in the same mm. Namespaces or containers may not prevent triggering if the relevant prctl and futex operations are exposed to the container workload. The issue is not network reachable. The affected subsystem is common, but the specific private hash resize path is a narrower futex feature and reliable triggering requires race timing. ## 4. Severity interpretation This behaves like a local DoS race, not an Important-class memory corruption issue. The realistic impact is an indefinitely blocked task, with possible system-wide panic only under hung-task panic configuration. Theoretical escalation is not supported because the patch only serializes inconsistent state observation and does not show stale object reuse, write-after-free, type confusion, callback control, or attacker-controlled memory reuse. ## 5. One-sentence report phrase A race in futex_pivot_pending during private futex hash resize can cause a local process to miss a completed pivot wakeup and remain stuck in uninterruptible sleep, potentially causing a kernel panic when hung task panic is enabled. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED. This is core futex synchronization code and a race condition, but the available evidence supports DoS only and does not justify treating it as memory corruption or privilege escalation. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: futex: Fix race in futex_pivot_pending() during private hash resize [ Upstream Commit: 4a7e941ca29a608c6244cbd028d3599ecaef7207 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a7e941ca29a608c6244cbd028d3599ecaef7207 Changed files: kernel/futex/core.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=4a7e941ca29a608c6244cbd028d3599ecaef7207 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80776 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80776 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:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 3 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).