From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72432][LOW] tpm_crb: Check ACPI_COMPANION() against NULL during probe [ Upstream Date: Sun, 16 Aug 2026 07:02:00 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72432 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: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: c041d2be785feb9b5e36331921eadaefbe65349d List-Id: CVE: CVE-2026-72432 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: tpm_crb: Check ACPI_COMPANION() against NULL during probe [ Upstream Commit: c041d2be785feb9b5e36331921eadaefbe65349d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c041d2be785feb9b5e36331921eadaefbe65349d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72432 Analysis date: Sun, 16 Aug 2026 07:02:00 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: `tpm_crb can dereference a missing ACPI companion when forced to bind to an unsuitable platform device via driver_override, allowing a local administrator or delegated device-management actor to trigger a kernel crash, with no evidence of confidentiality impact, integrity impact, or privilege escalation.` ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72432 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72432 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-2026-72432 LOW 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:N/A:H';**CWE-476;*CWE-20;CWE-703;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'tpm_crb assumed that a probed platform device always has an ACPI companion object. A local actor who can force driver binding through driver_override can make the platform driver match a device that is not backed by the expected ACPI data, which may lead to a NULL pointer dereference during probe and cause a kernel oops or crash. For the CVSS the PR:L is used in the paranoid score because some environments may delegate limited device management or sysfs binding control to a service account or reduced capability administrator, although PR:H is more typical on standard systems. The issue is not network reachable and requires local control over driver binding rather than packet input. Impact is denial of service only via kernel crash or oops, with no supported confidentiality or integrity impact from the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) SKIP CVE-2026-72432 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 48fe2cddc85c7849463bd01ae8b8c6b575ff508b YES NO NO unknown MAYBE SIMPLEFIX HARDWARE INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Conservative signals: * Reliable kernel crash / strong DoS: +1. Forced probing of `tpm_crb` against a non matching platform device without an ACPI companion can plausibly cause a NULL pointer dereference during probe. * Requires admin/root/CAP_* in typical deployments: -2. The practical trigger is `driver_override` or manual driver bind through sysfs, which is normally root/admin controlled. * Rare and difficult-to-reach path: -1. This is not normal TPM operation. It requires forced driver matching against an unsuitable device. Conservative raw result is negative, treated as 0 for practical bucket interpretation. Paranoid signals: * Reliable kernel crash / strong DoS: +1. A delegated device-management service account or reduced-capability admin could potentially trigger the bad bind in some environments. * No memory corruption bonus. The patch only supports a NULL companion validation failure and NULL dereference style crash, not UAF, OOB write, double free, type confusion, refcount abuse, or controlled overwrite. * No confidentiality or integrity impact. There is no supported leak, write primitive, credential access, TPM secret exposure, or privilege escalation path. * No network or firmware-mediated external influence. The affected path is local driver binding, not packet input or firmware-fed parsing. ## 3. Reachability analysis The bug is triggerable by a local actor able to force platform driver matching through `driver_override` or equivalent sysfs bind operations. In ordinary deployments this requires administrator privileges on the host. Namespaces or containers normally should not expose host driver binding controls, but a reduced-privilege device-management service or unusually delegated sysfs access could make the paranoid PR:L interpretation reasonable. The TPM CRB driver may be present on many systems, but the vulnerable condition is not default operation and depends on intentionally binding the driver to a device without the expected ACPI companion. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like local DoS issue, not an Important-class vulnerability. The realistic impact is a kernel oops or crash during probe. Theoretical severity does not extend beyond DoS based on the patch because the fix is a straightforward NULL check and there is no evidence of attacker-controlled memory reuse, stale pointer lifetime corruption, arbitrary write, information disclosure, or privilege escalation. ## 5. One-sentence report phrase `tpm_crb can dereference a missing ACPI companion when forced to bind to an unsuitable platform device via driver_override, allowing a local administrator or delegated device-management actor to trigger a kernel crash, with no evidence of confidentiality impact, integrity impact, or privilege escalation.` ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This is a local forced-driver-bind NULL dereference with admin-level reachability in normal deployments and no supported memory corruption or security-boundary bypass primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: tpm_crb: Check ACPI_COMPANION() against NULL during probe [ Upstream Commit: c041d2be785feb9b5e36331921eadaefbe65349d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c041d2be785feb9b5e36331921eadaefbe65349d Changed files: drivers/char/tpm/tpm_crb.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=c041d2be785feb9b5e36331921eadaefbe65349d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72432 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72432 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:L/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: 0 Paranoid ActionableScore: 1 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).