From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64322][MODERATE 7.0] udf: validate sparing table length as an entry count, not a byte count Date: Sat, 25 Jul 2026 11:27:36 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64322 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: 8 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: eeb0f3e193f8e523d03e4c9e084f6b4875f50e8e List-Id: CVE: CVE-2026-64322 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: udf: validate sparing table length as an entry count, not a byte count Commit: eeb0f3e193f8e523d03e4c9e084f6b4875f50e8e Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eeb0f3e193f8e523d03e4c9e084f6b4875f50e8e Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64322 Analysis date: Sat, 25 Jul 2026 11:27:36 -0400 ActionableScore: 8 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A crafted UDF filesystem image can abuse a sparing table length validation mismatch to trigger OOB reads and an OOB write in kernel UDF metadata handling, causing at least local DoS and plausibly enabling privilege escalation in environments where local users can cause UDF images to be mounted or automounted. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64322 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64322 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-2026-64322 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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-130;CWE-125;*CWE-787;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 filesystem image can pass sparing table validation because reallocationTableLen was checked like a byte count but later used as an entry count for st.mapEntry. This mismatch can make UDF code access up to several times beyond the accepted block size, causing out-of-bounds reads in udf_get_pblock_spar15 and an out-of-bounds write path through udf_relocate_blocks. For the CVSS the PR:L is used for the paranoid score because direct mounting normally requires administrator privileges, but local users may trigger filesystem mounting through delegated mount helpers, desktop automount, removable media workflows, or container and user namespace configurations. The issue is not network reachable in the normal model and requires a crafted local filesystem image. Impact is at least local denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact and possible privilege escalation due to kernel memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6) YES WRITE OOB DISK IMPROVEONLY LINUS KPANIC KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Memory corruption, strong corruption primitive: +2. The patch context explicitly describes OOB read and OOB write from treating `reallocationTableLen` as bytes during validation but as an entry count during later table walking. * Reliable kernel crash / strong DoS: +1. Crafted filesystem metadata can drive kernel parser accesses beyond the validated sparing table block. * Confidentiality impact plausible: +1. OOB read exists in `udf_get_pblock_spar15()` and `crc_itu_t()` can read beyond the block. * Integrity impact plausible: +1. `udf_relocate_blocks()` has an OOB write path via `memmove()` through `st->mapEntry[]`. * Important filesystem/storage path: +1. This is kernel filesystem metadata parsing during UDF mount/use. * Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. Direct mounting is normally privileged. * Corruption primitive somewhat constrained: -1. The write is tied to UDF sparing table layout and filesystem parser behavior, not an obvious arbitrary write primitive. Paranoid signals: * Local unprivileged trigger: +1. In practical desktop or delegated environments, crafted UDF media/images may be processed through automount, udisks/polkit, container mount delegation, or user namespace related workflows. * Memory corruption, strong corruption primitive: +2. The patch explicitly identifies OOB write, not just warning or validation cleanup. * Privilege escalation plausible: +2. Kernel filesystem parser OOB write from attacker-controlled on-disk metadata is a plausible LPE class even without a demonstrated exploit. * Reliable kernel crash / strong DoS: +1. Malformed metadata can plausibly crash the kernel during parsing or relocation paths. * Confidentiality impact plausible: +1. OOB read paths are explicitly described. * Integrity impact plausible: +1. OOB write path is explicitly described. * Important filesystem/storage path: +1. Filesystem metadata parsing bugs can have persistent or high-impact effects. * Corruption primitive somewhat constrained: -1. The exact overwrite target and payload control are not fully demonstrated. Call-site confidence: high. The commit message names the consuming paths `udf_get_pblock_spar15()`, `udf_relocate_blocks()`, `udf_update_tag()`, `crc_itu_t()`, and the OOB write sink. ## 3. Reachability analysis The bug is triggered by a crafted UDF filesystem image with a malformed sparing table. Direct exploitation usually requires the ability to mount or cause the kernel to parse that image, which is normally root or CAP_SYS_ADMIN controlled. However, local unprivileged reachability is plausible in environments with removable media automount, desktop storage helpers, delegated mount workflows, containers, or user namespace configurations. The issue is not realistically network reachable by itself. The affected path is not a core always-hit filesystem path, but UDF support is common enough that crafted media or images are a realistic exposure model. ## 4. Severity interpretation This is stronger than an ordinary Moderate because the patch context explicitly describes both OOB read and OOB write in kernel filesystem parsing. Conservative handling can score as borderline/actionable if only privileged manual mounting is considered. Paranoid handling should treat it as a Strong Important candidate because local user mediated mount paths are realistic on some systems and kernel OOB write from crafted filesystem metadata is a plausible privilege escalation class. Theoretical LPE is plausible, but not demonstrated as reliable from the provided patch. ## 5. One-sentence report phrase A crafted UDF filesystem image can abuse a sparing table length validation mismatch to trigger OOB reads and an OOB write in kernel UDF metadata handling, causing at least local DoS and plausibly enabling privilege escalation in environments where local users can cause UDF images to be mounted or automounted. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. This includes an explicit kernel OOB write primitive in filesystem parsing and plausible local-user reachability through automount or delegated mounting paths, so it should not be auto-closed. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: udf: validate sparing table length as an entry count, not a byte count Commit: eeb0f3e193f8e523d03e4c9e084f6b4875f50e8e Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eeb0f3e193f8e523d03e4c9e084f6b4875f50e8e Commit description: udf_load_sparable_map() accepts a sparing table when sizeof(*st) + le16_to_cpu(st->reallocationTableLen) > sb->s_blocksize is false, i.e. it treats reallocationTableLen as a number of BYTES that must fit in the block. But the table is walked as an array of 8-byte sparingEntry elements: for (i = 0; i < le16_to_cpu(st->reallocationTableLen); i++) { struct sparingEntry *entry = &st->mapEntry[i]; ... entry->origLocation ... } in udf_get_pblock_spar15() and udf_relocate_blocks(). A reallocationTableLen of N therefore passes the check whenever sizeof(*st) + N <= blocksize, yet the consumers index sizeof(*st) + N * sizeof(struct sparingEntry) bytes -- up to ~8x the block. On a crafted UDF image this is an out-of-bounds read in udf_get_pblock_spar15(); udf_relocate_blocks() additionally feeds the same length to udf_update_tag(), whose crc_itu_t() reads far past the block, and its memmove() through st->mapEntry[] is an out-of-bounds write. Validate reallocationTableLen as the entry count it is, with struct_size(). Fixes: 1df2ae3 ("udf: Fortify loading of sparing table") Cc: stable@vger.kernel.org Signed-off-by: Bryam Vargas Link: https://patch.msgid.link/20260612-b4-disp-91780c4e-v1-1-f15112ff6882@proton.me Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman 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=eeb0f3e193f8e523d03e4c9e084f6b4875f50e8e ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64322 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64322 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: 4 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: 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).