From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53117][MODERATE 7.0] s390/cio: use generic driver_override infrastructure [ Upstream Date: Thu, 25 Jun 2026 16:31:24 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53117 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: c4295487124f461405e1ef64dfa8c4ab0cb7ebcf List-Id: CVE: CVE-2026-53117 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: s390/cio: use generic driver_override infrastructure [ Upstream Commit: c4295487124f461405e1ef64dfa8c4ab0cb7ebcf Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c4295487124f461405e1ef64dfa8c4ab0cb7ebcf Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53117 Analysis date: Thu, 25 Jun 2026 16:31:24 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: NO Summary: A race in s390/cio driver_override handling can cause a use-after-free during css bus driver matching, allowing a local device-management actor to crash the kernel and requiring manual review for possible limited UAF impact beyond DoS. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53117 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53117 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-53117 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 's390/cio css bus matching can read driver_override without the device lock while another local control path changes or frees the override string. This creates a race based use after free in css_bus_match during driver probing and can crash the kernel through an invalid string access. For the CVSS the PR:L in the paranoid vector assumes a delegated or reduced capability administrator can write driver_override or trigger driver reprobe without full host root privileges. The issue is local and not network reachable. Impact is at least denial of service via kernel crash, with limited confidentiality or integrity impact only as a conservative UAF review assumption because the visible primitive is an unlocked stale pointer read rather than an arbitrary write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) MAYBE LOCK UAF HARDWARE LINUS MEMORY DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum** ## 2. Signal breakdown Conservative signals: * Generic memory corruption, UAF: +2. The match path can read `driver_override` without the device lock while another path replaces or frees it. * Real lifetime corruption: +1. This is a stale pointer after free caused by missing synchronization around `driver_override`. * Reliable kernel crash / strong DoS: +1. The likely failure mode is invalid string access in `strcmp()` during driver matching. * Privileged kernel/device-management memory corruption path: +1. The bug is in driver probing and bus matching for s390 CIO devices. * Availability impact realistic: +1. A successful trigger can crash the kernel or destabilize driver probing. * Hard or unreliable race: -1. The issue depends on a race between driver probing and override update/free. * Requires admin/root/CAP-like device control in typical deployments: -2. Writing driver override sysfs attributes and triggering reprobe is normally privileged. * Rare architecture/subsystem exposure: -1. This is specific to s390 CIO/css devices, not a broadly deployed generic Linux path. Paranoid additions/adjustments: * Local reduced-privilege trigger concern: +1. In some deployments, device-management operations may be delegated to container root, service accounts, or reduced-capability administrators. * Weak LPE concern: +1. The primitive is UAF, but visible use is stale string read/comparison rather than a demonstrated reclaim or write primitive. * Reduced privilege penalty instead of full admin penalty: use -1 instead of -2 for delegated-management environments. ## 3. Reachability analysis The bug is local and not network reachable. A realistic trigger requires access to s390 CIO/css device management, especially changing `driver_override` and causing driver matching or reprobe while `__driver_attach()` calls the bus match callback without the device lock. In normal host deployments this is administrator-controlled, so the conservative interpretation treats it as privileged. Namespaces or containers may matter only if device sysfs access or driver binding controls are delegated, in which case PR:L is a defensible paranoid interpretation. The path is not default-exposed on general Linux systems and is limited to s390 environments. ## 4. Severity interpretation This is not an ordinary cleanup bug because the commit explicitly fixes a UAF caused by unlocked lifetime handling. Realistic impact is most likely local DoS through a kernel crash during driver matching. Privilege escalation is not strongly demonstrated because the observed primitive is an unlocked stale pointer read in `strcmp()`, not an arbitrary write, controlled overwrite, or clear reclaim primitive. Still, because this is a kernel UAF in a privileged driver-management path, it should not be auto-closed as low-risk without manual review. ## 5. One-sentence report phrase A race in s390/cio driver_override handling can cause a use-after-free during css bus driver matching, allowing a local device-management actor to crash the kernel and requiring manual review for possible limited UAF impact beyond DoS. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the bug is a real UAF race in kernel driver matching, but exploitation appears local, timing-dependent, s390-specific, and typically privileged, with no demonstrated strong LPE primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: s390/cio: use generic driver_override infrastructure [ Upstream Commit: c4295487124f461405e1ef64dfa8c4ab0cb7ebcf Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c4295487124f461405e1ef64dfa8c4ab0cb7ebcf Changed files: drivers/s390/cio/cio.h drivers/s390/cio/css.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=c4295487124f461405e1ef64dfa8c4ab0cb7ebcf ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53117 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53117 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:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 3 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: NO 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).