From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53373][MODERATE REGULAR] mm/vma: do not try to unmap a VMA if mmap_prepare() invoked from mmap() [ Upstream Date: Sun, 19 Jul 2026 06:45:29 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53373 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: 5394bcb746503f2ae4b206212416dccea78e3773 List-Id: CVE: CVE-2026-53373 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: mm/vma: do not try to unmap a VMA if mmap_prepare() invoked from mmap() [ Upstream Commit: 5394bcb746503f2ae4b206212416dccea78e3773 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5394bcb746503f2ae4b206212416dccea78e3773 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53373 Analysis date: Sun, 19 Jul 2026 06:45:29 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: A local mmap path through stacked driver or filesystem compatibility handling can attempt to unmap an already detached VMA after an mmap action error, causing a kernel warning and possible local DoS on hardened systems. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53373 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53373 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-2026-53373 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:N/I:N/A:H';*CWE-664;*CWE-672;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'mmap_action_complete can be called from a compatibility mmap path where the VMA is not fully established in the maple tree and is already detached. If an mmap action returns an error, the old cleanup path can try to unmap that detached VMA even though the caller will clean it up, which can trigger a warning in vma_mark_detached. For the CVSS the PR:L is used because a local process must trigger the mmap path, but full administrative privileges are not clearly required. The issue is not network reachable and is driven by a local mmap operation through stacked driver or filesystem behavior. Impact is primarily denial of service through kernel warning or crash in hardened configurations such as panic_on_warn. No concrete UAF, OOB write, arbitrary write, or information leak primitive is demonstrated by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3) SKIP CVE-2026-53373 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: ac0a3fc9c07df79dc8a4ce9d274df00afc7bf12d YES NO NO unknown MAYBE READ WARNONLY TEST SYZBOT INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - 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 Triggered signals: * Local unprivileged trigger: +1 A local process can plausibly reach mmap paths without administrative privileges, depending on the stacked driver or filesystem involved. * Availability impact realistic: +1 The described symptom is a kernel warning in `vma_mark_detached()`. On hardened systems with `panic_on_warn`, this can become a local DoS. * Broad or core subsystem exposure: +1 The bug is in core MM/VMA mmap lifecycle handling, not an isolated leaf driver. Subtractors: * Special path or trigger conditions: -1 Triggering requires the compatibility mmap path from stacked drivers or filesystems, an mmap action error, and a detached not fully established VMA state. Paranoid-only signal: * Reliable kernel crash or strong DoS: +1 Counted only in the paranoid score because the provided evidence shows a warning, not a guaranteed default kernel crash. Not counted: * Generic memory corruption: +0 The patch does not show UAF, double free, OOB write, arbitrary write, type confusion, or attacker-controlled stale object reuse. * Privilege escalation plausible: +0 No concrete LPE primitive is demonstrated. * Confidentiality or integrity impact: +0 No leak, unauthorized write, page-cache corruption, or security-boundary bypass is shown. Call-site confidence: high. The relevant callers are visible: `__compat_vma_mmap()` now passes `is_compat=true`, while `__mmap_region()` passes `is_compat=false`. ## 3. Reachability analysis The bug is local-only and reached through mmap handling. A normal local process may be able to trigger the affected path if it can mmap an object handled through a stacked driver or filesystem path using the mmap compatibility layer. Namespaces or containers may matter because mmap is generally available inside containers, but the exact affected objects depend on mounted filesystems and driver exposure. No network trigger is evident. The path is core MM code, but the specific failing condition is not a generic mmap of every file. ## 4. Severity interpretation This behaves more like ordinary Moderate or Low-like DoS than Important. The realistic evidence is a warning caused by attempting to unmap an already detached VMA. The theoretical concern is that this is MM/VMA lifecycle code, but the patch context does not demonstrate memory corruption or a privilege escalation primitive. The paranoid score is raised only to keep the issue visible for manual review because core MM cleanup bugs can be subtle and `panic_on_warn` can convert the warning into a crash. ## 5. One-sentence report phrase A local mmap path through stacked driver or filesystem compatibility handling can attempt to unmap an already detached VMA after an mmap action error, causing a kernel warning and possible local DoS on hardened systems. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: core MM/VMA lifecycle bugs deserve review, but current evidence supports warning or DoS only, with no demonstrated UAF, stale reuse, arbitrary write, information leak, or privilege escalation path. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mm/vma: do not try to unmap a VMA if mmap_prepare() invoked from mmap() [ Upstream Commit: 5394bcb746503f2ae4b206212416dccea78e3773 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5394bcb746503f2ae4b206212416dccea78e3773 Changed files: include/linux/mm.h mm/util.c mm/vma.c tools/testing/vma/include/dup.h tools/testing/vma/include/stubs.h 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=5394bcb746503f2ae4b206212416dccea78e3773 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53373 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53373 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).