From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53015][LOW] erofs: unify lcn as u64 for 32-bit platforms [ Upstream Date: Mon, 06 Jul 2026 19:37:30 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53015 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: 4fc9b12e43a3f19a01a8fb61f7961be79de20253 List-Id: CVE: CVE-2026-53015 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: erofs: unify lcn as u64 for 32-bit platforms [ Upstream Commit: 4fc9b12e43a3f19a01a8fb61f7961be79de20253 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4fc9b12e43a3f19a01a8fb61f7961be79de20253 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53015 Analysis date: Mon, 06 Jul 2026 19:37:30 -0400 ActionableScore: 2 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A 32 bit truncation bug in EROFS compressed extent mapping can produce incorrect logical cluster addresses above the 4 GiB boundary on 32 bit platforms, but the issue is local, configuration dependent, and does not show a memory corruption or privilege escalation primitive. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53015 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53015 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-2026-53015 LOW CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L';CWE-190;CWE-681;CWE-682;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '3.6';DESCR 'A 32 bit truncation issue in EROFS zmap handling can occur because lcn was stored as unsigned long or unsigned int on 32 bit platforms. For large compressed EROFS images, shifting lcn by lclusterbits can wrap or truncate around the 4 GiB boundary and produce incorrect compressed extent mapping. This can lead to wrong file data being read or to filesystem errors when the kernel processes affected compressed extents. For the CVSS the PR:L in the paranoid score assumes a local user can cause a crafted EROFS image to be mounted or parsed through delegated mount rights, containerized administration, or an automount style workflow. The issue is not network reachable. Impact is limited to data integrity and availability of the mounted filesystem path, with no concrete evidence of UAF, OOB write, arbitrary write, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES DISK SIMPLEFIX LINUS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like** ## 2. Signal breakdown Conservative signals: * Important filesystem/storage path: +1. The bug affects EROFS compressed extent mapping in `fs/erofs/zmap.c`. * Integrity impact plausible: +1. Wrong `lcn` truncation can produce incorrect logical cluster mapping and wrong file data or filesystem consistency errors. * Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. Mounting EROFS images normally requires privileged mount capability. * Rare AND difficult-to-reach configuration: -1. The issue is limited to 32-bit platforms and large compressed EROFS images crossing the 4 GiB truncation boundary. Paranoid additional signal: * Local unprivileged trigger: +1. Only in environments with delegated mount, containerized administration, automount, or other workflows where a local user can cause a crafted EROFS image to be parsed. Not counted: * No generic memory corruption. The patch fixes integer width truncation, not UAF, OOB write, double free, type confusion, or arbitrary write. * No privilege escalation signal. No reclaim, overwrite, callback, refcount, or object confusion primitive is shown. * No remote reachability. This is filesystem image parsing/mapping, not a network-triggered path. * Availability impact not separately counted. Errors are plausible, but not shown as a reliable system-wide crash or persistent host-wide DoS. ## 3. Reachability analysis The realistic trigger is mounting or otherwise processing a large compressed EROFS image on a 32-bit kernel. In typical deployments this requires `CAP_SYS_ADMIN`, so conservative reachability is privileged local only. Namespaces or containers may lower practical reachability if a reduced-privilege actor can trigger mounts or if an automount pipeline processes attacker-supplied images, but that is configuration-dependent. The affected path is not network reachable and requires a specific 32-bit large-image condition. ## 4. Severity interpretation This behaves like a low-end Moderate or Low-like filesystem correctness issue, not an Important-class kernel vulnerability. The theoretical impact is incorrect extent calculation, wrong file data, or filesystem errors. The patch does not support memory corruption, page-cache corruption, arbitrary write, information disclosure, or privilege escalation. The paranoid score remains low because the strongest defensible concern is local processing of crafted filesystem metadata with limited integrity/availability impact. ## 5. One-sentence report phrase A 32 bit truncation bug in EROFS compressed extent mapping can produce incorrect logical cluster addresses above the 4 GiB boundary on 32 bit platforms, but the issue is local, configuration dependent, and does not show a memory corruption or privilege escalation primitive. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed or handled in deferred mode unless the product supports 32-bit kernels and mounts untrusted large EROFS images through delegated or automated workflows. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: erofs: unify lcn as u64 for 32-bit platforms [ Upstream Commit: 4fc9b12e43a3f19a01a8fb61f7961be79de20253 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4fc9b12e43a3f19a01a8fb61f7961be79de20253 Changed files: fs/erofs/zmap.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=4fc9b12e43a3f19a01a8fb61f7961be79de20253 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53015 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53015 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:H/PR:H/UI:N/S:U/C:N/I:L/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L The Best / paranoid CVSS score: 3.6 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).