From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98961][LOW] btrfs: unlock inode and extent in caller when io_uring read extent fails [ Upstream Date: Mon, 26 Oct 2026 14:58:20 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98961 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: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 2797eb38773a96914ccedeec71eb2144645400b2 List-Id: CVE: CVE-2026-98961 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: btrfs: unlock inode and extent in caller when io_uring read extent fails [ Upstream Commit: 2797eb38773a96914ccedeec71eb2144645400b2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2797eb38773a96914ccedeec71eb2144645400b2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98961 Analysis date: Mon, 26 Oct 2026 14:58:20 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A low-privilege Btrfs encoded-read allocation failure can leave inode and extent locks held, causing persistent local operation blockage without memory corruption. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98961 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98961 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-2026-98961 LOW https://www.kernelcve.org/list/?q=CVE-2026-98961 CHECK WITH IMPACT FROM ORIG NN NONE | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: 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:N/A:H';CWE-667;*CWE-772;CWE-459;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A synchronous failure in btrfs_uring_read_extent can leave the inode shared lock and extent lock held after btrfs_encoded_read has acquired them. The demonstrated trigger is failure to allocate the pages array, which can block later writes or overlapping extent operations and cause a persistent local availability loss. For the CVSS the PR:L value reflects that a local process must have access to the Btrfs file and the io_uring encoded read interface. AC:H reflects dependence on an allocation failure or memory pressure. The supported primitive is lock retention rather than UAF, OOB access, information disclosure, or memory corruption. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to LOW because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE LOCK DANGER DISK SIMPLEFIX ERRORPATH SKIP IO_URING V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 1 (+1 local low-privilege trigger, +1 persistent availability effect, -1 allocation-failure requirement). * Conservative score: 1; no floor or cap applied. * Raw paranoid score: 1; no stronger patch-supported consequence exists. * Paranoid score: 1. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Local unprivileged trigger: a process with access to the Btrfs file and encoded-read io_uring interface can invoke the failing operation; no host-administrator operation is shown. * +1 Availability impact: synchronous failure can retain the inode shared lock and extent lock, blocking later writes or overlapping extent operations. * -1 Hard/special trigger: the demonstrated path depends on failure to allocate the pages array, normally requiring memory pressure or allocation failure. * No UAF, OOB access, memory overwrite, authorization bypass, information disclosure, or ownership violation is shown. * No extra availability point: the retained-lock blockage is the single demonstrated consequence. * NEW52/B5-R does not apply: there is no retry-accumulated heap OOB write or subsequent consumption of corrupted structured state. * NEW53/B3-PENDING and NEW54/B4-PENDING do not apply: neither shared-backing modification nor a DENY-to-ALLOW authorization change exists. 3. Reachability analysis The caller already holds the inode and extent locks before entering `btrfs_uring_read_extent()`. A local process able to open the relevant Btrfs file and use the encoded-read io_uring command can reach the path without UID 0 or effective host-administrator power. No namespace capability, prior privileged setup, special hardware, or race is shown. Triggering the vulnerable return specifically requires an allocation failure, materially limiting reliability. 4. Primitive and severity reading The primitive is lock retention on a synchronous error path: one allocation-failure return omitted unlocks, while another failure path unlocked in the wrong layer. This is CLASS_C availability/invalid-state behavior, not a lifetime or memory-corruption primitive. The shown impact is operation blockage; host panic, filesystem corruption, confidentiality loss, and privilege escalation are unsupported. ImportantCandidate is therefore NO, and automatic Moderate/Low-like handling is permitted. 5. One-sentence report phrase A low-privilege Btrfs encoded-read allocation failure can leave inode and extent locks held, causing persistent local operation blockage without memory corruption. 6. Manual review advice NO MANUAL CHECK NEEDED The patch and call flow establish a constrained lock-leak availability defect with no unresolved corruption or security-boundary primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: btrfs: unlock inode and extent in caller when io_uring read extent fails [ Upstream Commit: 2797eb38773a96914ccedeec71eb2144645400b2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2797eb38773a96914ccedeec71eb2144645400b2 Changed files: fs/btrfs/ioctl.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=2797eb38773a96914ccedeec71eb2144645400b2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98961 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98961 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: 1 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).