From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-93243][LOW] mm/secretmem: properly account locked pages [ Upstream Date: Thu, 24 Sep 2026 12:35:38 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-93243 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: unknown X-AL-KERNEL-Commit: 853043cb129473ff2fa0090602be944d96b9d5c9 List-Id: CVE: CVE-2026-93243 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: mm/secretmem: properly account locked pages [ Upstream Commit: 853043cb129473ff2fa0090602be944d96b9d5c9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=853043cb129473ff2fa0090602be944d96b9d5c9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93243 Analysis date: Thu, 24 Sep 2026 12:35:38 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93243 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93243 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-2026-93243 LOW https://www.kernelcve.org/list/?q=CVE-2026-93243 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-400;CWE-770;CWE-693;BEST CVSS score: '5.5';DESCR 'A local user can bypass RLIMIT_MEMLOCK accounting for secretmem by mapping secret memory and then unmapping it while the underlying folios remain unevictable until inode destruction. Repeated map and unmap operations or fork related sharing can consume system memory with unreclaimable folios that are not represented in process RSS, reducing the ability of the OOM killer to select the responsible process. For the CVSS the PR:L is selected because exploitation requires a local process that can call memfd_secret and fault secretmem pages. The issue is not network reachable. Impact is system wide denial of service through memory exhaustion and instability. No confidentiality or integrity impact is supported because the patch does not indicate a memory corruption or information disclosure primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES READ DANGER INIT NOMEMCHK TEST IO_URING DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=NONE RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2 * Raw paranoid score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Local unprivileged trigger. The patch and commit establish that an ordinary local user can create secretmem mappings and bypass RLIMIT_MEMLOCK accounting through repeated map and unmap activity. CAP_IPC_LOCK is not required for the vulnerable bypass. * +1 Reliable host-wide denial of service. The commit explicitly states that repeated operations can consume all available system memory with unevictable folios and cause system instability. Folios are not represented in the responsible process RSS, reducing OOM killer effectiveness. * No separate resource-boundary bypass point awarded. RLIMIT_MEMLOCK bypass is the mechanism enabling the same resource-exhaustion outcome and is not counted independently. * No memory corruption signal. The patch does not establish UAF, double free, stale dereference, out-of-bounds access, arbitrary write, or type confusion. * No confidentiality or integrity signal. No disclosure, protected-data modification, page ownership violation, or privilege-escalation primitive is established. * No remote reachability signal. Exploitation requires local execution and use of memfd_secret. * No persistent reference-leak signal. The folios intentionally remain associated with the secretmem inode until inode destruction. The vulnerability is incorrect accounting rather than an unreleased kernel reference. * No paranoid increase. The demonstrated primitive remains resource exhaustion and does not support a stronger corruption or security-boundary interpretation. 3. Reachability analysis The evaluated attacker is an ordinary local user. The commit explicitly describes a user bypassing RLIMIT_MEMLOCK by mapping and unmapping secretmem ranges, or by sharing the secretmem file descriptor across forked processes. The complete trigger requires CONFIG_SECRETMEM support and local access to the memfd_secret syscall. No host-admin-equivalent privilege is required by the vulnerable accounting path. CAP_IPC_LOCK is specifically discussed because the fix removes its limit bypass, but the vulnerability is relevant to users operating within their normal RLIMIT_MEMLOCK constraints. No namespace-scoped capability is required for the demonstrated sequence. Namespace isolation is not the relevant access-control mechanism. No special hardware, race condition, privileged control-plane setup, or network exposure is established. 4. Primitive and severity interpretation The primitive is an accounting and resource-limiting failure. Secretmem folios are unevictable for the lifetime of the inode, while pre-fix RLIMIT_MEMLOCK accounting was tied to VMA mapping state. After munmap, VmLck no longer represented the secretmem allocation even though the folios remained allocated and unreclaimable. This is not an active stale-object lifetime bug. There is no UAF, post-free access, second release, refcount mutation through freed memory, arbitrary read or write, or security-sensitive object reinterpretation. The demonstrated consequence is host-wide memory exhaustion and resulting instability or denial of service after sustained local abuse. The patch does not support privilege escalation, information disclosure, integrity compromise, or persistent cross-user data modification. PrimitiveClass is NONE because no corruption, lifetime, authorization, ownership, or meaningful security-boundary primitive beyond resource accounting bypass is established. ImportantCandidate is NO because the issue is a resource exhaustion condition without evidence of memory corruption or a stronger exploitation path. AutoDowngradeAllowed is YES because the practical impact is sufficiently described as local resource-exhaustion DoS and no unresolved corruption primitive remains. 5. One-sentence report phrase A local user can bypass secretmem RLIMIT_MEMLOCK accounting through repeated map and unmap operations, causing unreclaimable folios to consume system memory and potentially result in host-wide denial of service. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch establishes a resource-accounting bypass leading to local denial of service, but no memory-corruption, authorization-bypass, confidentiality, integrity, or privilege-escalation primitive is present. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mm/secretmem: properly account locked pages [ Upstream Commit: 853043cb129473ff2fa0090602be944d96b9d5c9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=853043cb129473ff2fa0090602be944d96b9d5c9 Changed files: mm/20260813225328.2010303-1-4ncienth include/linux/sched/user.h mm/secretmem.c tools/testing/selftests/mm/memfd_secret.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=853043cb129473ff2fa0090602be944d96b9d5c9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93243 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93243 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: Not available 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: unknown 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).