From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68422][LOW] btrfs: fix root leak if its reloc root is unexpected in merge_reloc_roots() [ Upstream Date: Mon, 10 Aug 2026 12:04:01 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68422 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: b3d39b03799600c76c33486e2d29b73a771023db List-Id: CVE: CVE-2026-68422 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: btrfs: fix root leak if its reloc root is unexpected in merge_reloc_roots() [ Upstream Commit: b3d39b03799600c76c33486e2d29b73a771023db Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b3d39b03799600c76c33486e2d29b73a771023db Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68422 Analysis date: Mon, 10 Aug 2026 12:04:01 -0400 ActionableScore: 2 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A btrfs relocation error path may leak a btrfs_root reference when an unexpected reloc_root is encountered, causing a local resource leak and possible DoS only under privileged or unusual corrupted-filesystem conditions. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68422 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68422 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-2026-68422 LOW CHECK WITH IMPACT FROM ORIG NN NONE 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-772;*CWE-401;CWE-404;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A btrfs relocation error path can leak a btrfs_root reference when merge_reloc_roots encounters an unexpected reloc root and exits without dropping the root reference. This is a resource leak rather than a UAF or OOB memory corruption primitive. The realistic impact is local denial of service through accumulated leaked references or impaired cleanup after repeated relocation attempts on a corrupted or attacker controlled btrfs image. For the CVSS the PR:L paranoid interpretation is only for environments where non-admin service accounts or container roots can trigger btrfs relocation or operate on attacker controlled btrfs images. The issue is not network reachable and does not indicate confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES DISK SIMPLEFIX LEAK ERRORPATH SKIP 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 is in btrfs relocation code, which is part of filesystem metadata maintenance. * Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. Triggering relocation or operating on a corrupted btrfs filesystem normally requires administrative storage control. * Rare AND difficult-to-reach condition: -1. The error path requires an unexpected reloc_root, described as likely filesystem corruption such as a bad reloc tree key offset. Conservative result is floored at 0. Paranoid signals: * Important filesystem/storage path: +1. btrfs relocation is a storage metadata path. * Availability impact realistic: +1. Repeated triggering could leak btrfs_root references and cause resource retention or impaired cleanup. * Requires privileged or delegated storage control. No extra positive score unless the environment delegates btrfs operations to a reduced-privilege service or container root. No memory corruption signal is awarded. The patch fixes a missing btrfs_put_root() on an error path, i.e. a reference leak. It does not show UAF, double free, OOB access, stale callback, type confusion, arbitrary write, page-cache corruption, or credential/security-boundary bypass. ## 3. Reachability analysis The realistic trigger is local and storage-management related. An attacker would need the ability to mount or operate on a btrfs filesystem and reach relocation code with an unexpected reloc_root condition, likely involving corrupted metadata or a crafted filesystem image. In typical deployments this requires root or CAP_SYS_ADMIN. Namespaces or containers only matter if the product delegates real btrfs mount, balance, relocation, or block-device control to a reduced-privilege actor. There is no network reachability and no default remote attack surface. Call-site confidence: medium. The patch context shows the missing put in merge_reloc_roots(), but not all external ways to force the unexpected reloc_root condition. ## 4. Severity interpretation This behaves like a low-end resource leak / cleanup bug, not an Important-class kernel vulnerability. Theoretical impact is local DoS through accumulated leaked references, but realistic exploitation requires privileged or unusual storage control and a corrupted or attacker-controlled btrfs state. There is no supported privilege-escalation primitive. There is also no confidentiality or integrity impact indicated by the patch or by the affected operation. ## 5. One-sentence report phrase A btrfs relocation error path may leak a btrfs_root reference when an unexpected reloc_root is encountered, causing a local resource leak and possible DoS only under privileged or unusual corrupted-filesystem conditions. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed for urgent triage purposes unless the product exposes btrfs relocation or mounting of attacker-controlled images to untrusted users. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: btrfs: fix root leak if its reloc root is unexpected in merge_reloc_roots() [ Upstream Commit: b3d39b03799600c76c33486e2d29b73a771023db Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b3d39b03799600c76c33486e2d29b73a771023db Changed files: fs/btrfs/relocation.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=b3d39b03799600c76c33486e2d29b73a771023db ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68422 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68422 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: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: 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).