From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98834][MODERATE 7.0] mtd: core: avoid double-free of OTP NVMEM device [ Upstream Date: Sat, 24 Oct 2026 06:24:43 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98834 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: cecf007418b93a2cbc94269e07fe2fb28f54d8fb List-Id: CVE: CVE-2026-98834 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: mtd: core: avoid double-free of OTP NVMEM device [ Upstream Commit: cecf007418b93a2cbc94269e07fe2fb28f54d8fb Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cecf007418b93a2cbc94269e07fe2fb28f54d8fb Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98834 Analysis date: Sat, 24 Oct 2026 06:24:43 -0400 ActionableScore: 5 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: An OTP registration failure leaves a freed NVMEM device pointer live, enabling a later concrete double unregister and post-lifetime state mutation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98834 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98834 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 7.0 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-2026-98834 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98834 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=3 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/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:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'An OTP NVMEM registration error can unregister the user OTP device while leaving mtd otp_user_nvmem pointing to the released object. The caller or normal MTD teardown can then pass the stale pointer to nvmem_unregister again, creating a concrete double unregister and potential use after free or double free condition. For the CVSS the PR:H value is used because reliable attacker controlled triggering normally requires administrative control over MTD driver registration, removal, or device reprobe together with a suitable factory OTP setup failure. AC:H reflects the required error path and device lifecycle conditions. The demonstrated impact is primarily a kernel crash, while the paranoid score accounts for possible memory corruption if the freed NVMEM object is reused before the second unregister. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 6.4 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. No severity changing production threshold or specialist override was recorded. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. 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. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE DANGER ERRORPATH UAF HARDWARE LINUS KPANIC - - 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 the exact stale pointer reaches a second lifetime-ending unregister operation. * Raw paranoid score: 5. * Paranoid score: 5. No additional floor or cap changes it. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown * +2 Real UAF/lifetime violation: `nvmem_unregister()` may destroy the user OTP NVMEM object while `mtd->otp_user_nvmem` continues to reference it. * +1 Concrete repeated release: that exact uncleared field later reaches another `nvmem_unregister()` from caller error handling or normal teardown. * +1 Reliable kernel crash/strong DoS: double unregistering a freed NVMEM object plausibly faults or corrupts lifetime-management state. * Paranoid +1: the second unregister performs a write-like lifetime mutation through storage whose original object lifetime may have ended. * Raw base arithmetic: 2 + 1 + 1 = 4; FLOOR 5 changes 4 to 5. * Raw paranoid arithmetic: 2 + 1 + 1 + 1 = 5. The first unregister can end lifetime; the exact field survives; the second operation is a real unregister/lifetime mutation. Controlled reclaim, arbitrary write, disclosure, LPE, and separate C/I impact are not shown. No extra availability point is awarded for the same crash. 3. Reachability analysis The failure requires factory-OTP setup to fail after user-OTP registration. The patch establishes the ordered error/teardown sequence, not a timing race. Administrative MTD registration, removal, or reprobe is described as normally needed, but the supplied evidence does not prove that host-admin powers are invariably required or establish a below-host-admin trigger. Therefore host privilege, UID 0, and namespace-scoped reachability remain unknown. No rare-hardware or hard-race penalty is justified. 4. Primitive and severity reading This is an active structured NVMEM-device lifetime violation, not merely a shallow stale read. It is case B: first unregister may free the object, then a second unregister mutates lifetime state through the dangling pointer. That supports CLASS_B, not CLASS_A: useful reclaim, target control, and exploitation are unproven. The unresolved post-lifetime mutation requires Important-vs-Moderate review and prevents automatic downgrade. 5. One-sentence report phrase An OTP registration failure leaves a freed NVMEM device pointer live, enabling a later concrete double unregister and post-lifetime state mutation. 6. Manual review advice MANUAL CHECK REQUIRED Confirm trigger privileges and whether the second unregister can operate on reclaimed storage beyond producing a crash. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mtd: core: avoid double-free of OTP NVMEM device [ Upstream Commit: cecf007418b93a2cbc94269e07fe2fb28f54d8fb Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cecf007418b93a2cbc94269e07fe2fb28f54d8fb Changed files: drivers/mtd/mtdcore.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=cecf007418b93a2cbc94269e07fe2fb28f54d8fb ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98834 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98834 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:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 6.4 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: MODERATE KPANIC detected for this report: YES Published priority for this report (same as in Subject): MODERATE 7.0 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).