From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53369][LOW] udf: reject descriptors with oversized CRC length Date: Sun, 19 Jul 2026 05:52:02 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53369 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: 2 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: 832ab4a882dc9b3c0155490d9993642ef545fd22 List-Id: CVE: CVE-2026-53369 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: udf: reject descriptors with oversized CRC length Commit: 832ab4a882dc9b3c0155490d9993642ef545fd22 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=832ab4a882dc9b3c0155490d9993642ef545fd22 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53369 Analysis date: Sun, 19 Jul 2026 05:52:02 -0400 ActionableScore: 2 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like. Auto-close candidate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53369 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53369 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-2026-53369 LOW 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:L/UI:N/S:U/C:N/I:L/A:L';CWE-345;CWE-354;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '4.4';DESCR 'UDF descriptor parsing accepted a descriptor when descCRCLength plus the UDF tag size exceeded the block size, which skipped CRC validation and relied only on the weak 8 bit tag checksum. A crafted UDF filesystem image can use this to bypass descriptor integrity validation and have malformed or tampered metadata accepted during mount or metadata lookup. For the CVSS the PR:L is used for the paranoid score because some environments allow local users or delegated services to trigger filesystem mounts or automount removable media, while a normal server mount path often requires administrator privileges. The issue is not network reachable and does not show a direct memory corruption primitive in the patch context. Impact is primarily a low integrity validation bypass with possible limited availability impact if malformed metadata causes mount or filesystem handling errors.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Auto-close candidate (with actual score 1) YES DISK SIMPLEFIX LINUS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH NO NO guess ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=0 1. ActionableScore * Conservative score: 0 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like. Auto-close candidate** 2. Signal breakdown * Integrity impact plausible: +1. Oversized descCRCLength can bypass UDF descriptor CRC validation, allowing crafted metadata to be accepted based only on the weak 8-bit tag checksum. * Filesystem metadata validation concern: +1 in paranoid scoring only. A crafted filesystem image can influence UDF metadata parsing, but the patch does not show page-cache corruption, kernel memory corruption, or writes to privileged file-backed data. * Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2 in conservative scoring. Mounting arbitrary filesystem images normally requires privileged mount capability. * No memory corruption bonus. The patch rejects invalid metadata length before CRC handling and does not show UAF, OOB write, double-free, stale pointer reuse, arbitrary write, or type confusion. * No strong DoS bonus. The patch description does not demonstrate a reliable kernel crash, panic, filesystem shutdown, or persistent system-wide availability failure. 3. Reachability analysis The realistic trigger is a crafted UDF image processed during mount or metadata access. In normal server deployments, mounting such an image requires CAP_SYS_ADMIN or an equivalent privileged mount helper, so conservative reachability is privileged local. In desktop or removable-media environments, a local user may indirectly trigger parsing through automount or a delegated service, which supports the paranoid local-user interpretation. The issue is not network reachable unless a separate service accepts and mounts attacker-supplied UDF images. 4. Severity interpretation This behaves like an ordinary Moderate or Low-like validation flaw rather than an Important-class kernel vulnerability. The main effect is bypassing descriptor integrity validation for crafted UDF metadata. There is no concrete evidence of memory corruption, privilege escalation, sensitive data disclosure, or a reliable kernel crash. Theoretical downstream parser confusion is possible, but not supported by the shown patch context. 5. One-sentence report phrase A crafted UDF image can set an oversized descriptor CRC length to bypass CRC validation, causing malformed filesystem metadata to be accepted, but the patch context does not show memory corruption, privilege escalation, or reliable DoS. 6. Manual review recommendation NO MANUAL CHECK NEEDED. This can be handled as an auto-close candidate unless separate testing or external discussion demonstrates a concrete crash, memory corruption primitive, or security-boundary bypass. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: udf: reject descriptors with oversized CRC length Commit: 832ab4a882dc9b3c0155490d9993642ef545fd22 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=832ab4a882dc9b3c0155490d9993642ef545fd22 Commit description: udf_read_tagged() skips CRC verification when descCRCLength + sizeof(struct tag) exceeds the block size. A crafted UDF image can set descCRCLength to an oversized value to bypass CRC validation entirely; the descriptor is then accepted based solely on the 8-bit tag checksum, which is trivially recomputable. Reject such descriptors instead of silently accepting them. A legitimate single-block descriptor should never have a CRC length that exceeds the block. Fixes: 1da177e ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Assisted-by: Codex:gpt-5-4 Signed-off-by: Michael Bommarito Link: https://patch.msgid.link/20260413211240.853662-1-michael.bommarito@gmail.com Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman Changed files: fs/udf/misc.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=832ab4a882dc9b3c0155490d9993642ef545fd22 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53369 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53369 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:L/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L 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: 0 Paranoid ActionableScore: 2 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).