From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98855][IMPORTANT] of/overlay: put property on deadprops only after changeset add succeeds Date: Sat, 24 Oct 2026 10:30:22 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98855 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: d5151496a0a2b19c9c0c7b0ebf86b3de55a8fa3a List-Id: CVE: CVE-2026-98855 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: NO Patch: of/overlay: put property on deadprops only after changeset add succeeds Commit: d5151496a0a2b19c9c0c7b0ebf86b3de55a8fa3a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d5151496a0a2b19c9c0c7b0ebf86b3de55a8fa3a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98855 Analysis date: Sat, 24 Oct 2026 10:30:22 -0400 ActionableScore: 5 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: A failed overlay property addition leaves a freed property linked in `deadprops`, causing a concrete second free during aborted-node release. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98855 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98855 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-2026-98855 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-98855 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=3 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC) 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-415;*CWE-416;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A failed of_changeset_add_property operation can free a newly allocated property while its pointer remains linked in the deadprops list of a detached overlay node. Releasing the aborted node later frees the same property again, producing a concrete double free and potential use after free condition that can corrupt kernel heap state or crash the system. The base score uses PR:H because normal Device Tree overlay loading is an administrative operation and reliable triggering also appears to require a changeset allocation failure. For the CVSS the PR:L paranoid value reflects deployments where overlay management is delegated to a restricted service or reduced capability root context rather than unrestricted host administration. The paranoid impact accounts for a plausible privilege escalation path through heap corruption, but no reliable arbitrary write or proven exploitation chain is established by the available evidence. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage IMPORTANT to IMPORTANT because KP specialist did not establish a qualifying panic. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were TEMP_KPANIC_MERGE_IMPORTANT_WINS and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 1.9 and ActionableScore 3 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE ERRORPATH UAF IMPROVEONLY LINUS TEMP_KPANIC_MERGE_IMPORTANT_WINS KPANIC_UNSUPPORTED_REMOVED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 4. * Conservative score: 5. REAL UAF FLOOR 5 applies because an initial free can end `new_prop`’s lifetime, the exact pointer remains linked, and node release performs a second free. * Raw paranoid score: 5. * Paranoid score: 5. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown * +2 Real lifetime violation: the failed changeset path frees `new_prop` while `deadprops` retains its pointer. * +1 Concrete repeated release: `of_node_release()` later frees that exact dangling property again. * +1 Reliable kernel crash/strong DoS: a slab double free plausibly faults or corrupts allocator state. * Paranoid +1: the second `kfree`-equivalent operation acts on already-freed storage and can mutate allocator metadata; controlled reclaim or directed corruption is not shown. * No privilege penalty: Device Tree overlay loading is normally administrative, but the supplied patch does not establish the complete interface, capability check, or whether delegated management can reach this failure. * No timing penalty: allocation failure is a trigger constraint, not evidence of a narrow race. * No separate weak-LPE, structured-leverage, C/I, or extra availability points. Arbitrary write, controlled reclaim, chosen adjacent victim, and LPE are unproven. * B5-R and B3-PENDING do not apply; this is a double-free lifetime bug, not retry-accumulated OOB or shared-backing write. 3. Reachability analysis The actor must initiate overlay construction and reach an `of_changeset_add_property()` failure, apparently involving allocation failure. Normal overlay loading is commonly privileged, but exact UID/capability requirements and any delegated service path are absent. Namespace-scoped privilege, attacker control over allocation failure, prior setup, and reliable repeatability therefore remain unknown. 4. Primitive and severity reading This is concrete repeated lifetime corruption, not merely a stale cleanup read: the first error-path free can destroy the property, its exact pointer survives in `deadprops`, and node teardown performs a second lifetime-ending free. It is CLASS_B because heap corruption is credible but no controlled target, payload, reclaim, or exploitation chain establishes CLASS_A. The specific second free leaves material post-lifetime allocator-corruption leverage unresolved, so ImportantCandidate is YES and automatic downgrade is unsafe. 5. One-sentence report phrase A failed overlay property addition leaves a freed property linked in `deadprops`, causing a concrete second free during aborted-node release. 6. Manual review advice MANUAL CHECK REQUIRED Confirm the overlay privilege boundary, attacker influence over the failure condition, allocator behavior, and practical reuse potential. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: of/overlay: put property on deadprops only after changeset add succeeds Commit: d5151496a0a2b19c9c0c7b0ebf86b3de55a8fa3a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d5151496a0a2b19c9c0c7b0ebf86b3de55a8fa3a Commit description: add_changeset_property() links a new property of a not-yet-live target node into the node's deadprops list before handing it to of_changeset_add_property(). If that fails, the error path frees the property but leaves the freed pointer linked in deadprops, and of_node_release() frees it a second time when the aborted overlay's node is released. Record the changeset entry first and link the property into deadprops only on success. of_changeset_add_property() never looks at the node's property lists, so the order of the two steps is otherwise immaterial, and the error path frees a property that nothing references. Fixes: f962788 ("of: overlay: set node fields from properties when add new overlay node") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-fable-5 [Claude Code] Signed-off-by: Abdurrahman Hussain Link: https://patch.msgid.link/20260831-nh-of-alias-overlay-v7-4-02754604805a@nexthop.ai Signed-off-by: Rob Herring (Arm) Signed-off-by: Greg Kroah-Hartman Changed files: drivers/of/overlay.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=d5151496a0a2b19c9c0c7b0ebf86b3de55a8fa3a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98855 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98855 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:H/UI:N/S:U/C:L/I:L/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: unknown Paranoid ActionableScore: 5 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: NO 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).