From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80758][MODERATE 7.0] futex: Avoid private hash use-after-free on final put [ Upstream Date: Fri, 04 Sep 2026 12:20:34 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80758 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: dba60d26e9dda3e157ad6b0934d4232f6c6904ee List-Id: CVE: CVE-2026-80758 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: futex: Avoid private hash use-after-free on final put [ Upstream Commit: dba60d26e9dda3e157ad6b0934d4232f6c6904ee Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dba60d26e9dda3e157ad6b0934d4232f6c6904ee Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80758 Analysis date: Fri, 04 Sep 2026 12:20:34 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A race in futex_private_hash_put can drop the final reference to a private futex hash before reading fph mm, allowing a local unprivileged process to trigger a use-after-free read and likely kernel crash, with limited paranoid concern for broader UAF impact but no demonstrated privilege escalation primitive. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80758 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80758 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-2026-80758 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80758 CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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-416;CWE-362;CWE-825;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A use-after-free read can occur in futex_private_hash_put because futex_ref_put may drop the final reference to the private futex hash before the code reads the saved mm pointer. If the task is preempted after the final put, another task can switch to a replacement hash and the old hash can be freed after an RCU grace period, so the resumed task reads fph mm from freed memory. For the CVSS the PR:L is selected because a local unprivileged process is needed to create futex activity and reach the affected futex private hash path. The issue is not network reachable and requires local code execution. Impact is at least local denial of service via kernel crash or corrupted wakeup behavior. In the paranoid interpretation it may allow limited confidentiality or integrity impact due to kernel use-after-free behavior and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES UAF LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP YES 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 * Local unprivileged trigger: +1. Futex paths are reachable by local user processes without requiring root privileges. * Memory corruption, weak primitive: +1. This is a real UAF read, but under the Race-UAF downgrade rule it is not treated as a strong corruption primitive because the patch only shows a stale read of `fph->mm`, not write-after-free, type confusion, callback control, or controlled reclaim. * Real lifetime corruption: +1. The bug is a reference lifetime issue where the final put can allow the private hash object to be freed before `fph->mm` is read. * Reliable kernel crash / strong DoS: +1. KASAN reports slab-use-after-free, and the stale read can plausibly lead to kernel crash or corrupted wakeup behavior. * Broad/default/common subsystem: +1. Futex is a core Linux synchronization API broadly reachable by ordinary local applications. * Hard or unreliable race / special timing required: -1. Triggering requires a preemption window after final reference drop and concurrent replacement/free after an RCU grace period. * Paranoid manual-review uplift: +1. Because this is a real UAF in a broad futex path, the paranoid score is raised to the Race-UAF cap for triage sensitivity, but without claiming a proven LPE primitive. Conservative total: 4. Paranoid total: 5. ## 3. Reachability analysis A local unprivileged process can plausibly reach the affected futex private hash path through futex activity. The issue is not network reachable and requires local code execution. Namespaces do not remove the basic local reachability because futex is a common per-process synchronization interface, although exact triggering may depend on whether the private hash resize path is available and exercised. Realistic exploitation requires winning a narrow race involving final reference drop, preemption, replacement hash pivot, RCU grace period, and later stale read. Call-site confidence: medium. The affected function and immediate lifetime sequence are visible, but broader call paths and practical trigger reliability are inferred from futex subsystem behavior and the commit message. ## 4. Severity interpretation This behaves stronger than an ordinary Moderate because it is a confirmed kernel UAF in a broad local API, not just a warning or validation bug. Realistic evidence supports local DoS and corrupted wakeup behavior. Theoretical LPE concern exists only as a cautious UAF triage concern, because the patch does not show attacker-controlled reclaim, stale object reuse as another type, write-after-free, function pointer dispatch, or refcount takeover. Therefore it is best treated as Actionable Moderate rather than a Strong Important candidate. ## 5. One-sentence report phrase A race in futex_private_hash_put can drop the final reference to a private futex hash before reading fph mm, allowing a local unprivileged process to trigger a use-after-free read and likely kernel crash, with limited paranoid concern for broader UAF impact but no demonstrated privilege escalation primitive. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK. Reason: confirmed UAF plus broad futex reachability should not be auto-closed, even though the demonstrated primitive is weak and race-dependent. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: futex: Avoid private hash use-after-free on final put [ Upstream Commit: dba60d26e9dda3e157ad6b0934d4232f6c6904ee Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dba60d26e9dda3e157ad6b0934d4232f6c6904ee 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=dba60d26e9dda3e157ad6b0934d4232f6c6904ee ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80758 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80758 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: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: 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: NO 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).