From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98528][MODERATE REGULAR] gpio: cdev: fix kernel stack leak to user-space in error path [ Upstream Date: Mon, 19 Oct 2026 02:01:09 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98528 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: 2 X-AL-KERNEL-Commit: 8460ee5216ab9a38263b01dca4b0a27e083f70f3 List-Id: CVE: CVE-2026-98528 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: gpio: cdev: fix kernel stack leak to user-space in error path [ Upstream Commit: 8460ee5216ab9a38263b01dca4b0a27e083f70f3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8460ee5216ab9a38263b01dca4b0a27e083f70f3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98528 Analysis date: Mon, 19 Oct 2026 02:01:09 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A failed GPIO chip guard acquisition can leave a stack allocated line information structure uninitialized and expose stale kernel stack contents through the version 1 GPIO cdev ioctl. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98528 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98528 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-2026-98528 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98528 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, 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:N/A:N';*CWE-457;*CWE-200;CWE-908;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '4.7';DESCR 'A kernel stack information leak can occur in the GPIO character device path because gpio_desc_to_lineinfo() may return before initializing the line information structure when the GPIO chip guard cannot be acquired. In the version 1 ioctl path, an uninitialized gpio_v2_line_info object can then be converted and copied to user space, potentially exposing stale kernel stack contents. For the CVSS the PR:L value is used because a local user or process must be able to access the GPIO character device and issue the relevant ioctl. AC:H reflects the need to reach the error path while the GPIO chip is being removed or is otherwise no longer available. The issue is not network reachable. Impact is an information disclosure with no demonstrated write primitive, kernel crash, or direct privilege escalation. The paranoid score raises confidentiality to C:H because leaked kernel stack values may include sensitive pointers or other data useful for weakening kernel protections. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold 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 INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE LEAK ERRORPATH HARDWARE LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 PrimitiveClass=CLASS_B RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=REQUIRED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 2. * Conservative score: 2. No floor or cap applied. * Raw paranoid score: 3. * Paranoid score: 3. No floor or cap applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Conservative signals: * +1 Concrete disclosure path. An uninitialized stack resident `gpio_v2_line_info` can reach `gpio_v2_line_info_to_v1()` and then `copy_to_user()`. * +1 Confidentiality plausible. The commit explicitly identifies leakage of kernel stack contents to userspace. Paranoid signal: * +1 Potential security value of disclosed stack data. The copied fields may contain kernel pointers or other values useful for weakening address randomization, but the exact exposed bytes and repeatability are not established. No negative points were applied: * The timing penalty was withheld because guard acquisition failure is established, but the evidence does not show that the required removal window is narrow or difficult to repeat. * A host-admin penalty was withheld because permissions for the GPIO character device and control over chip removal are unresolved. * No rare-hardware penalty was applied merely because GPIO hardware is involved. Important non-awarded signals: * No UAF, OOB write, arbitrary write, controlled reclaim, authorization bypass, kernel crash, or privilege escalation is demonstrated. * Local unprivileged reachability is not awarded because possession of an appropriate GPIO cdev file descriptor and control over the complete failure sequence are not established. * B5-R does not apply because there is no retry-accumulated heap OOB write. * B3-PENDING does not apply because there is no shared-backing write. * B4-PENDING does not apply because no authorization decision changes from DENY to ALLOW. 3. Reachability analysis A local process must access the GPIO character device and invoke the version 1 line-information ioctl. The vulnerable copy occurs when `gpio_desc_to_lineinfo()` cannot acquire the GPIO chip guard, normally because the chip is concurrently disappearing or is no longer registered. The supplied evidence does not establish whether an ordinary user can open the relevant device node or independently cause GPIO chip removal. Consequently, effective host-administrator requirements remain unknown. GPIO cdev access is not inherently user-namespace or network-namespace scoped, so `NamespaceScopedPrivilege=NO`. No remote trigger is present. The issue depends on GPIO cdev version 1 support and an applicable GPIO device, but this alone does not justify a niche-hardware penalty. Race difficulty and practical repeatability require manual confirmation. 4. Primitive and severity interpretation The exact primitive is a kernel-to-userspace disclosure of uninitialized stack contents. In `lineinfo_get_v1()`, `lineinfo_v2` is a local stack object. Before the fix, failed guard acquisition returned without initializing that object. Its fields could then be converted into the version 1 result and copied to userspace. This is not a UAF or memory-write corruption. It is a concrete information-disclosure primitive classified as `CLASS_B` because disclosure is established, while its size, content, repeatability, and security leverage remain unresolved. The demonstrated consequence is disclosure of stale kernel stack bytes. Potential exposure of useful kernel pointers is plausible but not confirmed. `ImportantCandidate=NO` because substantial repeatable disclosure, a privilege-escalation chain, or another Important-grade consequence is not established. `ManualReview=REQUIRED` because the exact fields copied by `gpio_v2_line_info_to_v1()`, device permissions, trigger control, and repeatability determine whether this is merely a limited leak or a practical KASLR-bypass primitive. `AutoDowngradeAllowed=YES` because no unresolved memory-corruption or authorization-boundary primitive is present, but downgrade should follow that review. 5. One-sentence report phrase A failed GPIO chip guard acquisition can leave a stack allocated line information structure uninitialized and expose stale kernel stack contents through the version 1 GPIO cdev ioctl. 6. Manual review recommendation MANUAL CHECK REQUIRED Verify the exact bytes copied to userspace, whether kernel pointers can be disclosed, whether repeated reads are possible, and whether a below-host-admin user can reach the guard-failure condition. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: gpio: cdev: fix kernel stack leak to user-space in error path [ Upstream Commit: 8460ee5216ab9a38263b01dca4b0a27e083f70f3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8460ee5216ab9a38263b01dca4b0a27e083f70f3 Changed files: drivers/gpio/gpiolib-cdev.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=8460ee5216ab9a38263b01dca4b0a27e083f70f3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98528 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98528 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:L/I:N/A:N The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N The Best / paranoid CVSS score: 4.7 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: 2 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).