From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53295][LOW] mailbox: add sanity check for channel array [ Upstream Date: Fri, 26 Jun 2026 16:24:09 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53295 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: 5cc3300fab262b26c28bc2fc06df693410c3840b List-Id: CVE: CVE-2026-53295 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: mailbox: add sanity check for channel array [ Upstream Commit: 5cc3300fab262b26c28bc2fc06df693410c3840b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5cc3300fab262b26c28bc2fc06df693410c3840b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53295 Analysis date: Fri, 26 Jun 2026 16:24:09 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53295 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53295 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-2026-53295 LOW CHECK 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-476;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'A missing sanity check in mbox_controller_register() allowed a mailbox controller to be registered with a nonzero channel count but without a valid channel array. Later code could dereference the missing channel array and trigger an OOPS, which may be hard to notice when mailbox controllers are instantiated very early during boot. For the CVSS the PR:H means the attacker typically needs administrative control over kernel driver loading or an already running faulty or malicious mailbox controller driver. The issue is not network reachable and is not exposed through a normal remote protocol. Impact is denial of service via kernel OOPS or boot time crash, with no supported confidentiality or integrity impact from the shown primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) YES SIMPLEFIX LINUS NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 1. ActionableScore * Conservative score: 0 * Paranoid score: 0 * Final recommended bucket: **Ordinary Moderate / Low-like** 2. Signal breakdown * Reliable kernel crash / strong DoS: +1. A missing `mbox->chans` check can lead to a later NULL pointer dereference and OOPS. * Requires admin/root/CAP_SYS_ADMIN/CAP_NET_ADMIN in typical deployments: -2. Triggering requires registering a malformed mailbox controller, normally possible only from kernel driver code or by loading/modifying a kernel module. * No remote reachable signal. The mailbox controller registration path is not exposed through a network protocol. * No local unprivileged trigger. There is no normal syscall, netlink, ioctl, or procfs path that lets an unprivileged user provide this malformed `struct mbox_controller`. * No memory corruption bonus. The concrete primitive is NULL pointer dereference, not UAF, OOB write, double free, refcount misuse, or type confusion. * No confidentiality or integrity impact. The patch only prevents dereferencing a missing channel array. 3. Reachability analysis The bug is reachable when a mailbox controller driver calls `mbox_controller_register()` with `num_chans` set but `chans == NULL`. In normal deployments this is a driver correctness issue rather than an attacker-controlled interface. An attacker would typically need administrative control over kernel module loading, a malicious or broken in-kernel driver, or a faulty platform integration. Namespaces and containers do not meaningfully reduce the privilege requirement because mailbox controller registration is not delegated to container users. The path may execute early during boot, so the OOPS can be hard to observe, but that does not improve attacker reachability. 4. Severity interpretation This behaves like a low-end DoS-only kernel bug. The theoretical impact is a kernel OOPS or boot-time crash if a malformed mailbox controller is registered. There is no realistic evidence of privilege escalation, information disclosure, writable stale object access, or attacker-controlled memory corruption. This should not be treated as an Actionable Moderate or Important candidate. 5. One-sentence report phrase A missing sanity check in `mbox_controller_register()` can allow a malformed mailbox controller with no channel array to trigger a NULL pointer dereference and OOPS, but exploitation normally requires privileged kernel driver control and has DoS-only impact. 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is an internal driver-registration NULL pointer dereference with PR:H, no network exposure, no unprivileged trigger, and no supported memory-corruption or privilege-escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mailbox: add sanity check for channel array [ Upstream Commit: 5cc3300fab262b26c28bc2fc06df693410c3840b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5cc3300fab262b26c28bc2fc06df693410c3840b Changed files: drivers/mailbox/mailbox.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=5cc3300fab262b26c28bc2fc06df693410c3840b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53295 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53295 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:L 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).