From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45991][IMPORTANT] udf: fix partition descriptor append bookkeeping [ Upstream Date: Wed, 27 May 2026 17:49:40 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45991 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 8 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: 058b451b1039f056d1362c4fec2229e522366ab0 List-Id: CVE: CVE-2026-45991 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: udf: fix partition descriptor append bookkeeping [ Upstream Commit: 058b451b1039f056d1362c4fec2229e522366ab0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=058b451b1039f056d1362c4fec2229e522366ab0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45991 Analysis date: Wed, 27 May 2026 17:49:40 -0400 ActionableScore: 8 ActionableScore lower bound: 5 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45991 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45991 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: IMPORTANT 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-2026-45991 IMPORTANT CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-122;*CWE-20;CWE-131;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A crafted UDF image with repeated partition descriptors can make handle_partition_descriptor() append duplicate entries without recording partnum, causing num_part_descs and allocation capacity tracking to diverge. The growth path was sized from partnum while inserts used num_part_descs, so a full table could be reallocated without enough capacity and the next append could write past the heap allocation. For the CVSS the PR:L is used in the paranoid score because crafted filesystem images may be mounted through automount, delegated mount helpers, removable media workflows, or containerized environments, although typical direct mounting requires administrator privileges. The issue is not network reachable. Impact is at least local denial of service and in the worst case may allow confidentiality or integrity impact because the bug is a heap out of bounds write in filesystem mount parsing.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) MAYBE WRITE OOB DISK SIMPLEFIX LINUS KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=5 1. ActionableScore * Conservative score: 5 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: 2. Signal breakdown * Generic memory corruption, strong primitive: +2. The patch description explicitly states a heap out-of-bounds write in `part_descs_loc[]`. * Privilege escalation plausible: +2 in paranoid view. Heap OOB writes in filesystem parsers can sometimes be shaped into stronger primitives, although no controlled overwrite target is demonstrated here. * Reliable kernel crash / strong DoS: +1. A heap OOB write during mount can plausibly crash the kernel. * Important filesystem/storage path: +1. The bug is in UDF filesystem mount parsing. * Integrity impact plausible: +1. Heap metadata or adjacent kernel objects may be corrupted. * Local unprivileged trigger in some deployments: +1. Crafted UDF images may be processed by automount, removable media workflows, mount helpers, or delegated/container mount paths. * Requires admin/root in conservative deployments: -2. Direct mounting of arbitrary UDF images normally requires `CAP_SYS_ADMIN`. 3. Reachability analysis The primary trigger is mounting a crafted UDF filesystem image with repeated partition descriptors. On hardened systems, direct mounting is root-only. However, practical exposure can be lower privilege when removable media, desktop automount, containerized mount workflows, loop-mount services, or privileged helpers process user-supplied images. The issue is not network reachable by itself. Exploitation conditions are realistic wherever untrusted UDF images can be mounted or auto-mounted. 4. Severity interpretation This is a real heap OOB write, not a WARN-only filesystem issue. Conservative handling is Actionable Moderate because typical direct mount requires admin privileges. Paranoid handling is a Strong Important candidate because filesystem image parsers are common attack surfaces in automount/removable-media scenarios and heap OOB writes can be underestimated during early triage. Practical LPE is not proven, but manual review is required. 5. One-sentence report phrase A crafted UDF image with repeated partition descriptors can desynchronize descriptor deduplication and capacity tracking, causing a heap out-of-bounds write during filesystem mount parsing. 6. Manual review recommendation MANUAL CHECK REQUIRED. This is an explicit heap OOB write in a filesystem parser, with plausible lower-privilege exposure through automount or delegated mount workflows even though direct mounting is usually privileged. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: udf: fix partition descriptor append bookkeeping [ Upstream Commit: 058b451b1039f056d1362c4fec2229e522366ab0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=058b451b1039f056d1362c4fec2229e522366ab0 Changed files: fs/udf/super.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=058b451b1039f056d1362c4fec2229e522366ab0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45991 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45991 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:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.8 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: 5 Paranoid ActionableScore: 8 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).