From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80929][MODERATE 7.0] sysctl: move the "cad_pid" entry from pid_table[] to kern_reboot_table[] Date: Fri, 11 Sep 2026 17:18:59 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80929 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: 6 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: e8527de7fea191fda704792a56081f9009aeec37 List-Id: CVE: CVE-2026-80929 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: sysctl: move the "cad_pid" entry from pid_table[] to kern_reboot_table[] Commit: e8527de7fea191fda704792a56081f9009aeec37 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8527de7fea191fda704792a56081f9009aeec37 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80929 Analysis date: Fri, 11 Sep 2026 17:18:59 -0400 ActionableScore: 6 ActionableScore lower bound: 5 Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80929 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80929 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-2026-80929 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80929 CHECK WITH IMPACT FROM ORIG NN LOW 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:L/A:H';CWE-284;CWE-269;CWE-863;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '6.1';DESCR 'A namespace permission bug allowed cad_pid to be modified from a child pid/user namespace even though cad_pid is a global kernel setting used by the root namespace reboot path. A local non root user could create namespaces and gain sufficient rights inside the child namespace to write this sysctl, causing a mismatch between namespace scoped permissions and global kernel state. For the CVSS the PR:L is used because local code execution by an unprivileged user is required, but full host root privileges are not required in configurations that allow unprivileged user namespaces. The issue is not network reachable and is triggered through local sysctl access rather than packet processing. Impact is mainly an integrity and availability policy bypass, not memory corruption. The realistic impact is limited because an observable effect normally depends on the Ctrl Alt Del or reboot related path using cad_pid.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6) SKIP CVE-2026-80929 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE LINUS BOOT KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=5 PrimitiveClass=CLASS_A RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=YES ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 5 * Conservative score: 5. No floor or cap applied. * Raw paranoid score: 6 * Paranoid score: 6. No floor or cap applied. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown Conservative signals: * +2 Concrete authorization decision bypass. The cad_pid sysctl controlled global reboot related state but was placed under pid_table permissions, allowing a non-root user with a child pid/user namespace to modify it. * +1 Local unprivileged trigger. The commit explicitly states that a non-root user can unshare pid/user namespaces and modify cad_pid from the child namespace. * +1 Cross-boundary isolation/policy bypass. Namespace-scoped permissions were able to affect a global kernel setting used by the root namespace reboot path. * +1 Integrity plausible. The attacker can modify a global kernel policy/state variable that should only be controlled by GLOBAL_ROOT_UID. Paranoid additional signal: * +1 Availability plausible. Misconfiguration of cad_pid can affect the Ctrl-Alt-Del or reboot related signal path, potentially disrupting intended system management behavior, although this depends on that path being exercised. Non-awarded signals: * RealUAF not awarded. No use-after-free, stale object, double release, or lifetime corruption is shown. * Memory corruption not awarded. The patch moves a sysctl entry and does not establish OOB, UAF, arbitrary write, or controlled kernel corruption. * Remote reachability not awarded. The issue is local sysctl and namespace control-plane access, not packet-triggered behavior. * Sensitive FD/resource theft not awarded. No downstream protected file descriptor, credential, or secret access is established. * Practical root LPE not awarded. The patch establishes unauthorized global state modification, but not a complete root privilege escalation chain. * Reliable kernel crash not awarded. No kernel crash, panic, or memory fault is shown. * Race/timing penalty not applied. This is not a timing race. * Host-admin penalty not applied. The supplied evidence positively states non-root namespace-based modification is possible. 3. Reachability analysis A local non-root user can reach the vulnerable path when unprivileged user namespace creation is available. The attacker can unshare pid/user namespaces, become root within the child namespace, and write the cad_pid sysctl because it was incorrectly exposed through pid_table permissions. The complete relevant operation is namespace-scoped according to the commit text, so HostAdminRequired=NO and NamespaceScopedPrivilege=YES. There is no direct network trigger. There is no special hardware requirement. There is no race requirement. The main deployment dependency is whether unprivileged user namespaces are enabled and whether the CAD/reboot-related path is operationally relevant on the system. 4. Primitive and severity interpretation The exact primitive is an authorization and namespace-boundary bypass: a child namespace root can modify a global sysctl that should be readable or writable only by GLOBAL_ROOT_UID. This is not memory corruption and not a UAF. The demonstrated consequence is unauthorized modification of global reboot-related kernel state. PrimitiveClass=CLASS_A because the patch directly restores a mandatory authority boundary by moving cad_pid from pid_table to kern_reboot_table, ensuring only global root can read or modify it. ImportantCandidate=YES because this is a concrete security-boundary bypass affecting global kernel state from a below-host-admin actor. AutoDowngradeAllowed=NO because automatically closing it as ordinary low risk would lose an established namespace-to-global authorization bypass. Operationally, this is best treated as Actionable Moderate with Important-class review sensitivity. It is not a strong memory-corruption issue, but it is a real namespace permission bug with global kernel-state impact. 5. One-sentence report phrase A local non-root user can use pid/user namespaces to modify the global cad_pid sysctl, bypassing the intended GLOBAL_ROOT_UID restriction and potentially affecting root namespace reboot or Ctrl-Alt-Del handling. 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a concrete namespace-to-global authorization bypass, not just a harmless sysctl placement cleanup, and the real impact depends on system namespace policy and CAD/reboot handling. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: sysctl: move the "cad_pid" entry from pid_table[] to kern_reboot_table[] Commit: e8527de7fea191fda704792a56081f9009aeec37 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8527de7fea191fda704792a56081f9009aeec37 Commit description: cad_pid is global, and kill_cad_pid() is only used in the root namespace. However, due to pid_table_root_permissions(), a non-root user can unshare pid/user namespaces and modify it from the child namespace. This makes no sense and is simply wrong. Move it to kern_reboot_table[] where it logically belongs; this ensures that only GLOBAL_ROOT_UID can read/modify this sysctl. Note that this patch doesn't preserve "#ifdef CONFIG_PROC_SYSCTL" around the "cad_pid"; CONFIG_PROC_SYSCTL selects CONFIG_SYSCTL, so it is always set when kern_reboot_table[] is compiled. Cc: stable@vger.kernel.org Fixes: e054bcb ("sysctl: move cad_pid into kernel/pid.c") Signed-off-by: Oleg Nesterov Acked-by: Alexey Gladkov Reviewed-by: Bradley Morgan Reviewed-by: Pavel Tikhomirov Signed-off-by: Joel Granados Signed-off-by: Greg Kroah-Hartman Changed files: kernel/pid.c kernel/reboot.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=e8527de7fea191fda704792a56081f9009aeec37 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80929 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80929 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:L/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H The Best / paranoid CVSS score: 6.1 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: 5 Paranoid ActionableScore: 6 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).