From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53085][IMPORTANT] bpf: fix mm lifecycle in open-coded task_vma iterator [ Upstream Date: Fri, 26 Jun 2026 08:39:01 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53085 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 7 X-AL-KERNEL-ActionableScore-Lower: 6 X-AL-KERNEL-Commit: 239cec25a22662dbd80f57d94b38178c8be95269 List-Id: CVE: CVE-2026-53085 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: bpf: fix mm lifecycle in open-coded task_vma iterator [ Upstream Commit: 239cec25a22662dbd80f57d94b38178c8be95269 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=239cec25a22662dbd80f57d94b38178c8be95269 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53085 Analysis date: Fri, 26 Jun 2026 08:39:01 -0400 ActionableScore: 7 ActionableScore lower bound: 6 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A BPF `task_vma` iterator can race with task exit and use a freed `mm_struct` because it reads `task->mm` without taking an `mmget()` reference, allowing local BPF-capable attackers to trigger kernel crash and potentially creating a privilege-escalation-relevant UAF condition. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53085 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53085 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: IMPORTANT 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-2026-53085 IMPORTANT CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;*CWE-833;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'The BPF task_vma open coded iterator can race with task exit because it reads task mm without taking an mm reference. If the target task exits concurrently, mm_struct can be freed while the iterator still uses it, creating a use after free in the VMA iteration path. For the CVSS the PR:L is selected because reliable triggering requires local ability to run or load a BPF program that can use this iterator, but this may be available to a non root user, a delegated BPF capable service, or a reduced capability container context. The issue is not network reachable and requires local execution context. Impact is at least local denial of service via kernel crash or deadlock, and in the paranoid case may allow confidentiality and integrity impact due to kernel memory corruption from the UAF. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) MAYBE READ LOCK DEADLOCK BPF ERRORPATH UAF DMAorINTERRUPT HARDWARE LINUS KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=6 ## 1. ActionableScore * Conservative score: 6 * Paranoid score: 7 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown * Local BPF-capable trigger: +1 Triggering requires local ability to run or load a BPF program using the open-coded `task_vma` iterator. This is not remote, but may be reachable by non-root users or reduced-capability service/container contexts depending on BPF policy. * Generic memory corruption, strong corruption primitive: +2 The commit explicitly describes a use-after-free of `mm_struct` because `task->mm` is read without `mmget()` and the task may exit concurrently. * Real lifetime corruption: +1 This is a real reference-lifetime bug: missing `mmget()` allows `mm_struct` to be freed while still used by the iterator. * Weak LPE concern: +1 A kernel UAF on `mm_struct` in a BPF-controlled iterator path is security-relevant. No concrete reclaim or write primitive is shown, so this is not strong LPE by itself, but privilege escalation is plausible enough for manual review. * Local high-control kernel data-plane API: +1 BPF is a rich local kernel API with attacker-shaped program behavior and object/lifetime interactions. * Reliable kernel crash / strong DoS: +1 The UAF can plausibly crash the kernel. The patch also addresses deadlock risk from IRQ-disabled contexts. * Hard or timing-dependent race: -1 The UAF requires racing iterator setup/use against task exit, so exploitation reliability is not trivial. * Broad/common subsystem exposure: +1 in paranoid score only BPF is widely deployed, but this specific open-coded iterator/kfunc path is narrower than generic syscall exposure. This raises the paranoid score from 6 to 7. ## 3. Reachability analysis The bug is locally reachable by a user or process able to execute BPF programs that can use the `task_vma` iterator kfuncs. In hardened distributions, unprivileged BPF is often disabled and BPF loading may require `CAP_BPF`, `CAP_PERFMON`, `CAP_SYS_ADMIN`, or equivalent policy. However, this should not be treated as full host-root in all deployments because BPF capability may be delegated to services, observability agents, container contexts, or reduced-capability root. The issue is not network reachable. Namespaces and containers matter because delegated BPF capability or relaxed unprivileged BPF settings can reduce the practical privilege requirement. Realistic exploitation requires local execution plus a race with task exit, but the affected object is `mm_struct`, and the patch explicitly confirms a UAF due to missing reference acquisition. ## 4. Severity interpretation This is more than ordinary Moderate because it is a real kernel lifetime bug in a high-risk local API. The directly demonstrated impact is local DoS through kernel crash or deadlock. The theoretical higher impact is privilege escalation through UAF exploitation, but the patch does not show a concrete reclaim, arbitrary write, or controlled overwrite primitive. Conservative handling: Actionable Moderate. Paranoid handling: Strong Important candidate, because BPF plus `mm_struct` UAF is historically worth manual review even when exploitation is not demonstrated. ## 5. One-sentence report phrase A BPF `task_vma` iterator can race with task exit and use a freed `mm_struct` because it reads `task->mm` without taking an `mmget()` reference, allowing local BPF-capable attackers to trigger kernel crash and potentially creating a privilege-escalation-relevant UAF condition. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is explicit UAF/lifetime corruption in a BPF path, with plausible but not proven privilege-escalation potential. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: fix mm lifecycle in open-coded task_vma iterator [ Upstream Commit: 239cec25a22662dbd80f57d94b38178c8be95269 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=239cec25a22662dbd80f57d94b38178c8be95269 Changed files: kernel/bpf/task_iter.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=239cec25a22662dbd80f57d94b38178c8be95269 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53085 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53085 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:H/I:H/A:H The Best / paranoid CVSS score: 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: 6 Paranoid ActionableScore: 7 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).