From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-97906][LOW] bootconfig: Fix integer overflow in initrd size check [ Upstream Date: Sat, 26 Sep 2026 14:12:11 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-97906 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 8d4343a411eaa182d323ab5b149496416015f27d List-Id: CVE: CVE-2026-97906 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: bootconfig: Fix integer overflow in initrd size check [ Upstream Commit: 8d4343a411eaa182d323ab5b149496416015f27d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d4343a411eaa182d323ab5b149496416015f27d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97906 Analysis date: Sat, 26 Sep 2026 14:12:11 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97906 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97906 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: LOW 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-2026-97906 LOW https://www.kernelcve.org/list/?q=CVE-2026-97906 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';CWE-190;CWE-125;*CWE-20;BEST CVSS score: '4.4';DESCR 'A crafted bootconfig footer in an initrd can provide a very large size value that causes pointer subtraction to wrap before the bounds check in get_boot_config_from_initrd. The kernel can then pass an invalid address and an attacker controlled length to xbc_calc_checksum during early boot, causing an out of bounds read and a fatal page fault that prevents the system from booting. For the CVSS the PR:H rating reflects that reliable triggering requires modification of the initrd or another trusted boot artifact, which normally requires administrator, bootloader, physical, or provisioning infrastructure control. The issue is not network reachable by itself. Impact is denial of service during boot. The available code does not establish an information disclosure, write, memory corruption, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES OOB INIT LINUS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=YES NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: -1 * Conservative score: 0 * Raw paranoid score: -1 * Paranoid score: 0 * Applied conservative floor/cap: score normalized from -1 to 0 because ActionableScore cannot be negative. * Applied paranoid floor/cap: score normalized from -1 to 0 because ActionableScore cannot be negative. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Reliable kernel crash / strong DoS. A crafted initrd footer can cause pointer arithmetic wraparound and make xbc_calc_checksum read from an invalid address for up to 4 GB. The supplied context explicitly states that this causes a fatal page fault during early boot and prevents the kernel from booting. * -2 Full host-admin-equivalent prerequisite. Reliable triggering requires modifying the initrd image or another trusted boot artifact. Such modification normally requires host root, bootloader control, physical boot-media control, or control of privileged provisioning infrastructure. Important non-awarded signals: * +0 Weak invalid-read concern. The patch establishes an out of bounds read, but not an attacker-useful disclosure, write, control-flow effect, or post-read security-sensitive behavior. * Controlled reclaim is not demonstrated. * Arbitrary or directed kernel write is not demonstrated. * Memory corruption is not demonstrated. The established primitive is an invalid read followed by a fatal fault. * Confidentiality is not awarded because xbc_calc_checksum does not return the read data to an attacker-visible interface. * Integrity is not awarded because no write into kernel memory, files, credentials, or policy state is shown. * Remote reachability is not established. The crafted input is consumed from an initrd during local early boot, not directly from network traffic. * Local unprivileged trigger is not established. An ordinary local user cannot normally alter the boot initrd or its bootconfig footer. * Namespace-scoped privilege is not applicable. Initrd construction and boot artifact selection are host-level boot operations. * No race, UAF, refcount mutation, repeated release, RCU lifetime violation, callback control, or security-boundary bypass is established. * No extra Availability point is awarded because the fatal boot page fault is already counted as the single reliable DoS signal. 3. Reachability analysis The evaluated attacker is a host boot-artifact modifier, not an ordinary local user, container user, network-namespace administrator, or remote network peer. The vulnerable input is the bootconfig footer embedded in the initrd. The kernel processes it in get_boot_config_from_initrd during early boot, before normal userspace is available. A reliable trigger therefore requires an attacker to provide a modified initrd through a privileged channel such as root-controlled initramfs generation, bootloader configuration, boot media replacement, physical access, or compromised provisioning or network-boot infrastructure. No relevant operation is namespace-scoped. A user namespace, network namespace, delegated capability, or container root does not normally permit replacement of the host boot initrd or control of the host bootloader input. No special hardware or timing race is required once a malicious initrd can be supplied. A network provisioning environment could distribute a malicious initrd, but that would require compromise or control of the provisioning path. It is not direct network reachability of the vulnerable kernel function. 4. Primitive and severity interpretation The exact primitive is an integer-underflow or pointer-wrap validation failure. The bootconfig size is read as an untrusted 32 bit value from the initrd footer. Before the fix, the code subtracts that value from the footer address before proving that the subtraction remains inside the initrd range. On affected 32 bit conditions, a size such as 0xFFFFFFFF can wrap the pointer. The later comparison against initrd_start can then fail to detect that the calculated address is invalid. xbc_calc_checksum subsequently dereferences the invalid address and attempts to scan a very large range, resulting in an early-boot page fault. This is not an active structured stale-object issue, a UAF, a refcount problem, or a repeated-release condition. It is a direct invalid-read and crash path. The demonstrated consequence is a denial of service because the host may fail to boot. The speculative consequence would be only an internal read of unintended mapped memory, but the patch context does not establish an attacker-visible disclosure channel, a write primitive, or meaningful post-read control. PrimitiveClass is CLASS_C because the established behavior is crash and DoS through invalid-state pointer arithmetic rather than a reusable kernel corruption or ownership primitive. ImportantCandidate is NO because there is no demonstrated controlled corruption, security-boundary bypass, memory write, disclosure, lifetime violation, or below-host-admin trigger. AutoDowngradeAllowed is YES because the issue is a constrained boot-artifact validation failure with host-admin-equivalent prerequisites and a demonstrated crash-only outcome. Likely operational severity is low for ordinary deployed systems. The issue should still be fixed through normal kernel maintenance on systems that boot initrds supplied by external provisioning or image-distribution infrastructure. 5. One-sentence report phrase A malformed bootconfig footer in a host-controlled initrd can cause pointer arithmetic wraparound and an early boot kernel page fault, resulting in denial of service but requiring privileged control of the boot artifact. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch establishes an invalid-read early-boot crash but does not establish a memory-write, disclosure, UAF, authorization bypass, privilege-escalation path, or below-host-admin trigger. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bootconfig: Fix integer overflow in initrd size check [ Upstream Commit: 8d4343a411eaa182d323ab5b149496416015f27d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d4343a411eaa182d323ab5b149496416015f27d 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=8d4343a411eaa182d323ab5b149496416015f27d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97906 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97906 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: Not available The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.4 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: 0 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).