From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-93182][MODERATE REGULAR] sched/fair: Fix overflow in update_tg_cfs_runnable() [ Upstream Date: Thu, 17 Sep 2026 22:10:11 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-93182 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: unknown X-AL-KERNEL-Commit: 39d707097a0820c6e87eff4195f0940e8ff1147e List-Id: CVE: CVE-2026-93182 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: sched/fair: Fix overflow in update_tg_cfs_runnable() [ Upstream Commit: 39d707097a0820c6e87eff4195f0940e8ff1147e Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=39d707097a0820c6e87eff4195f0940e8ff1147e Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93182 Analysis date: Thu, 17 Sep 2026 22:10:11 -0400 ActionableScore: 3 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93182 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93182 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-2026-93182 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-93182 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-190;CWE-369;CWE-682;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A u32 overflow in update_tg_cfs_runnable() can corrupt CFS runnable_sum accounting when runnable_avg is multiplied by divider. The corrupted scheduler accounting can propagate into group load values and eventually make div_u64() hit a divide by zero path during task dequeue or scheduling activity, causing a kernel crash. For the CVSS the PR:L reflects that a local process can generate scheduler load and task group activity in plausible deployments without full administrator privileges. The issue is not network reachable and requires local execution on the affected host. Impact is denial of service through a kernel crash. There is no clear UAF, OOB access, information leak, or arbitrary write primitive in the provided patch context, so confidentiality and integrity impact are not raised.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES DANGER UAF KERNEL_PANIC_PLUS_UAF HARDWARE DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 3 * Conservative score: 3 * Raw paranoid score: 3 * Paranoid score: 3 * Final recommended bucket: **Borderline / manual review recommended**:: No floor or cap was applied. 2. Signal breakdown Positive signals: * +1 Local unprivileged trigger: the vulnerable path is ordinary scheduler activity. The supplied crash was observed while running hackbench and no host-admin-only interface is required by the visible call path. * +1 Reliable kernel crash / strong DoS: the supplied trace shows divide-by-zero in scheduler code leading to a kernel crash path. * +1 Broad/default/common subsystem exposure: CFS scheduler accounting is a core kernel path and is broadly deployed. Non-awarded signals: * +0 Real UAF: no use-after-free or stale post-lifetime object use is established. * +0 Strong corruption primitive: the bug corrupts scheduler accounting values, but no controlled overwrite, arbitrary write, controlled reclaim, type confusion, or callback control is shown. * +0 Confidentiality impact: no disclosure path is established. * +0 Integrity impact: no unauthorized modification of protected data or credentials is established. * +0 Extra availability: not awarded because the same kernel crash is already counted once. * +0 Race/timing penalty: this is not a timing race. It is an arithmetic overflow and propagation sequence. * +0 Host-admin penalty: host-admin-equivalent privilege is not positively established. * +0 Rare subsystem penalty: scheduler CFS accounting is not a niche or rare path. * Concrete repeated release/refcount: not present. No first release can end lifetime, no exact stale reference survives, no second lifetime/refcount mutation exists, and no repeated-release floor applies. 3. Reachability analysis The likely attacker is a local user or local process that can generate scheduler load and task-group activity. The supplied trace uses UID 0, but the visible vulnerable operation is normal task scheduling and the call path does not show a privileged ioctl, sysctl, module load, or host-admin-only configuration step. Namespace-scoped privilege is not relevant to the trigger as supplied. No complete namespace capability chain is needed or shown. Prior host setup is limited to having the affected scheduler configuration and task-group accounting enabled in the kernel, which is a common deployment condition rather than a special hardware or physical-access requirement. No direct network reachability is established. A remote attacker would need some separate ability to execute workload on the host, so the vulnerability is local from this evidence. There is no race window to win. The crash occurs through arithmetic overflow and later propagation into invalid load accounting. 4. Primitive and severity interpretation The exact primitive is an integer overflow in `update_tg_cfs_runnable()` where `se->avg.runnable_avg * divider` was computed into a `u32`. The overflow can corrupt scheduler runnable/load accounting and later produce an invalid `gcfs_rq->load.weight` value. That corrupted accounting can reach `div_u64()` as a zero divisor after truncation, causing a kernel crash. This is an active kernel bookkeeping corruption, but it is not a demonstrated memory-corruption primitive in the exploitability sense. There is no UAF, OOB access, arbitrary write, controlled reclaim, refcount takeover, or security-boundary bypass in the supplied patch context. PrimitiveClass is CLASS_C because the demonstrated behavior is crash/DoS from invalid scheduler state. ImportantCandidate is NO because no meaningful exploitation leverage beyond crash is established. AutoDowngradeAllowed is YES because the issue is suitable for ordinary Moderate-style handling after review, although the core scheduler location and host-wide crash make manual review recommended rather than unnecessary. 5. One-sentence report phrase A u32 overflow in CFS group runnable accounting can corrupt scheduler load values and later trigger a divide-by-zero in the scheduler, allowing a local workload to crash the kernel without evidence of UAF, information disclosure, or privilege escalation. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the demonstrated impact is a host-wide kernel crash in core scheduler code, but the patch does not establish a memory corruption, lifetime, authorization, or privilege-escalation primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: sched/fair: Fix overflow in update_tg_cfs_runnable() [ Upstream Commit: 39d707097a0820c6e87eff4195f0940e8ff1147e Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=39d707097a0820c6e87eff4195f0940e8ff1147e Changed files: kernel/sched/fair.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=39d707097a0820c6e87eff4195f0940e8ff1147e ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93182 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93182 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: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: 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).