From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45948][LOW] ext4: fix memory leak in ext4_ext_shift_extents() Date: Wed, 27 May 2026 19:54:14 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45948 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: unknown X-AL-KERNEL-Commit: 7e807cb8603b7664fa630a696cd891d9a03c248d List-Id: CVE: CVE-2026-45948 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: ext4: fix memory leak in ext4_ext_shift_extents() Commit: 7e807cb8603b7664fa630a696cd891d9a03c248d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7e807cb8603b7664fa630a696cd891d9a03c248d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45948 Analysis date: Wed, 27 May 2026 19:54:14 -0400 ActionableScore: 2 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-2026-45948 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45948 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-2026-45948 LOW CHECK 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:N/A:H';*CWE-401;*CWE-772;CWE-404;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'ext4_ext_shift_extents() can return directly on an unexpected missing extent without releasing the path allocated by ext4_find_extent(). A local user may exercise the extent shifting path through file range operations on an already mounted ext4 filesystem, but reliable triggering requires corrupted or inconsistent extent metadata. For the CVSS the PR:L is used because the operation can be reached by a local file writer on an affected mount, while creating the corrupted filesystem state usually requires separate conditions or administrator controlled image setup. The issue is not network reachable and does not provide a memory corruption primitive. Impact is availability only through a memory leak if the error path can be triggered repeatedly.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) MAYBE DISK SIMPLEFIX LEAK IMPROVEONLY - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 1. ActionableScore * Conservative score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: 2. Signal breakdown * Local trigger: +1. A local user with write access may reach extent shifting operations on an already mounted ext4 filesystem. * Availability/resource leak concern: +1. The error path leaks the extent path allocated by `ext4_find_extent()`. * Important filesystem/storage path: +1. The code is in ext4 extent manipulation. * Hard/specific condition: -1. Triggering requires an unexpected missing extent, usually corrupted or inconsistent extent metadata. * Resource leak only cap. No UAF, OOB, arbitrary write, data leak, or privilege escalation is shown. * No network reachability. 3. Reachability analysis The affected path is local and can be exercised through ext4 extent-shifting operations such as file range manipulation on a mounted ext4 filesystem. However, the actual leak path requires corrupted or inconsistent extent metadata where `extent == NULL` unexpectedly. Creating that state typically requires separate corruption, crafted image setup, or administrator-controlled conditions. It is not remotely reachable. 4. Severity interpretation This is a low-risk resource leak on an ext4 corruption error path. The realistic impact is memory leakage if the path can be triggered repeatedly. There is no memory corruption primitive, information disclosure, integrity impact, or LPE evidence. 5. One-sentence report phrase `ext4_ext_shift_extents()` can leak an extent path on an `EFSCORRUPTED` error path when unexpected missing extent metadata is encountered. 6. Manual review recommendation NO MANUAL CHECK NEEDED. This is an availability-only memory leak on a corrupted metadata path, with no demonstrated security-boundary bypass or memory corruption primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ext4: fix memory leak in ext4_ext_shift_extents() Commit: 7e807cb8603b7664fa630a696cd891d9a03c248d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7e807cb8603b7664fa630a696cd891d9a03c248d Commit description: In ext4_ext_shift_extents(), if the extent is NULL in the while loop, the function returns immediately without releasing the path obtained via ext4_find_extent(), leading to a memory leak. Fix this by jumping to the out label to ensure the path is properly released. Fixes: a18ed35 ("ext4: always check ext4_ext_find_extent result") Signed-off-by: Zilin Guan Reviewed-by: Zhang Yi Reviewed-by: Baokun Li Link: https://patch.msgid.link/20251225084800.905701-1-zilin@seu.edu.cn Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: fs/ext4/extents.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=7e807cb8603b7664fa630a696cd891d9a03c248d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45948 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45948 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:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 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).