From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99075][LOW] rust_binder: reschedule node refcount update on thread exit Date: Mon, 26 Oct 2026 15:52:55 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99075 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: 71cbad138969edecef01b28dff87d91b56db538d List-Id: CVE: CVE-2026-99075 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: rust_binder: reschedule node refcount update on thread exit Commit: 71cbad138969edecef01b28dff87d91b56db538d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=71cbad138969edecef01b28dff87d91b56db538d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99075 Analysis date: Mon, 26 Oct 2026 15:52:55 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A Binder thread exit can discard a pending node refcount notification and permanently retain the node, causing a local resource leak without demonstrated memory corruption or authorization bypass. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99075 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99075 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-2026-99075 LOW https://www.kernelcve.org/list/?q=CVE-2026-99075 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: 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:L';*CWE-772;CWE-404;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.3';DESCR 'The bug is a Binder node lifecycle and resource retention issue rather than demonstrated memory corruption. BINDER_THREAD_EXIT can cancel a pending node refcount increment and leave the delivery state inconsistent with the count state, preventing the node from being removed from the owning process node tree after external references are dropped. For the CVSS the PR:L value is used because a local process with Binder access must create the node activity and cause the relevant thread to exit. The base score uses AC:H because triggering depends on a pending deferred refcount update being assigned to the exiting thread. The demonstrated impact is limited availability loss through persistent per process node retention, with no supported UAF, OOB access, information leak, or write primitive. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 3.3 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE DANGER INIT UAF LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 2. * Conservative score: 2; no floor or cap applied. * Raw paranoid score: 2. * Paranoid score: 2; no stronger patch-supported primitive exists. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Local below-host-admin trigger: supplied evidence supports a local process with Binder access creating the relevant node activity and invoking `BINDER_THREAD_EXIT`. * +1 Concrete persistent kernel resource/reference retention: cancellation drops delivery of a pending refcount increment, desynchronizing delivery/count state and potentially leaving the node permanently in the process node tree. * No timing penalty: exit must occur with deferred work pending, but the evidence does not establish a narrow or externally uncontrollable race. * No additional availability point: accumulation into material host-wide exhaustion is not demonstrated. * No UAF, OOB access, repeated release, arbitrary write, controlled reclaim, disclosure, protected-state corruption, or authorization bypass is shown. * NEW52/B5-R and NEW53/B3-PENDING do not apply: there is no OOB write or shared-backing write. 3. Reachability analysis The supported actor is a below-host-admin local process with Binder access; host UID 0 is not required. Binder device access and applicable policy remain deployment prerequisites, but no host-admin operation, special hardware, namespace-scoped capability, or prior privileged per-object setup is shown. The actor can influence thread exit and node activity, although reliably arranging a pending deferred increment may require sequencing or timing. Namespace capability scope is not relevantly established. 4. Primitive and severity reading The exact defect is cancellation-induced lifecycle bookkeeping desynchronization resulting in persistent node retention. It is passive invalid/resource state, not stale post-lifetime access or memory corruption, so `CLASS_C` is appropriate. The demonstrated effect is per-process resource leakage; broad exhaustion or host failure is unproven. There is no DENY-to-ALLOW authorization decision or protected-resource access. Consequently this is not an Important candidate and can be auto-downgraded. 5. One-sentence report phrase A Binder thread exit can discard a pending node refcount notification and permanently retain the node, causing a local resource leak without demonstrated memory corruption or authorization bypass. 6. Manual review advice NO MANUAL CHECK NEEDED The patch establishes only constrained lifecycle/resource retention with no unresolved corruption or trust-boundary primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: rust_binder: reschedule node refcount update on thread exit Commit: 71cbad138969edecef01b28dff87d91b56db538d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=71cbad138969edecef01b28dff87d91b56db538d Commit description: When a thread exits via BINDER_THREAD_EXIT, its pending work items are cancelled. If a thread exits while holding a pending node refcount increment (e.g. pushed as deferred work to that thread), the refcount increment was previously dropped because Node::cancel() and NodeWrapper::cancel() were no-ops. Dropping the refcount update leaves the node's delivery state and count state desynchronized, and userspace will not receive the notification, which can cause the node to never be freed from the process's nodes tree when all external references are dropped. Fix this by implementing DeliverToRead::cancel() for Node and NodeWrapper to move the pending refcount update to the process's work queue on thread exit so another thread can deliver it to userspace. Cc: stable Fixes: eafedbc ("rust_binder: add Rust Binder driver") Signed-off-by: Alice Ryhl Link: https://patch.msgid.link/20260903-binder-thread-exit-node-v1-1-be09ff14f6a4@google.com [ Dropped first argument in calls to `push_work()` to adjust to the existing form without mainline commit dbb17c9 ("rust_binder: move (e)poll wait queue to Process"). - Miguel ] Signed-off-by: Miguel Ojeda Signed-off-by: Greg Kroah-Hartman Changed files: drivers/android/binder/node.rs drivers/android/binder/node/wrapper.rs 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=71cbad138969edecef01b28dff87d91b56db538d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99075 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99075 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:L/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS score: 3.3 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).