From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99265][MODERATE 7.0] io_uring/openclose: keep the lock in io_pipe_fixed() Date: Tue, 03 Nov 2026 22:29:52 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99265 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 4 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: b4b7b2d19dab611f3cf3d052aa19278e7e4c4683 List-Id: CVE: CVE-2026-99265 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: io_uring/openclose: keep the lock in io_pipe_fixed() Commit: b4b7b2d19dab611f3cf3d052aa19278e7e4c4683 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b4b7b2d19dab611f3cf3d052aa19278e7e4c4683 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99265 Analysis date: Tue, 03 Nov 2026 22:29:52 -0400 ActionableScore: 4 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: A fault-and-reuse race lets an unprivileged io_uring process remove an unrelated replacement file from its active fixed-file table. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99265 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99265 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: MODERATE 7.0 Manual review required: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-99265 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99265 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) 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:H';CWE-362;CWE-367;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.3';DESCR 'io_pipe_fixed could drop uring_lock after installing pipe files and before copying slot numbers to user memory. If copy_to_user faults while another request closes and reuses either slot, cleanup can remove the unrelated replacement file from the fixed file table. The concrete primitive is synchronized removal of the wrong file table entry rather than UAF, OOB access, or arbitrary memory corruption. For the CVSS the PR:L value is used because a local user or process must submit io_uring requests and control the faulting user pointer. AC:H reflects the required io_wq execution and race with slot reuse. Impact is low integrity and availability loss in the affected ring, with possible stronger service disruption when a fixed file table is shared. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 4 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. KP and FD specialist checks stage MODERATE_KPANIC to MODERATE because KP specialist did not establish a qualifying panic. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.8 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 4) MAYBE SIMPLEFIX LEAK ERRORPATH IO_URING INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 PrimitiveClass=CLASS_B RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 4. * Conservative score: 4; no floor or cap applied. * Raw paranoid score: 4. * Paranoid score: 4; no additional speculative boundary or memory-corruption points. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown * +2 — Attacker-influenced active structured-state corruption: cleanup removes the file currently occupying a reused fixed-file slot, rather than the pipe file installed by this request. * +1 — Local unprivileged trigger: ordinary io_uring submission, a faulting userspace pointer, and concurrent close/update/open operations are supported by the supplied evidence. * +1 — Availability impact: removal of an unrelated fixed-file registration can disrupt subsequent operations using the ring. * +1 — Concrete practical chain: install pipe entries → unlock → slot close/reuse → `copy_to_user()` fault → remove replacement entry. * -1 — Material race complexity: execution through io-wq and successful slot reuse during the unlocked interval are required. No UAF, heap OOB write, arbitrary kernel write, controlled reclaim, confidentiality impact, host crash, or LPE is shown. B5-R and B3-PENDING do not apply. There is no authorization DENY-to-ALLOW change, so B4-PENDING does not apply. 3. Reachability analysis A local non-root process can create and operate its own io_uring, control the faulting destination, and submit the competing fixed-file operations. No capability, namespace privilege, host setup, special hardware, or boot option is identified. The race requires io-wq execution and timely reuse, but the attacker can repeatedly submit the relevant operations. Cross-principal use through a shared or delegated ring is credible but not established. 4. Primitive and severity reading The primitive is wrong-object removal from an active fixed-file table: the unlocked error path acts on a slot whose ownership may have changed. This is CLASS_B structured resource/lifetime corruption, not a memory UAF or OOB write. The immediate proven effect is loss of an unrelated registration and ring-level disruption. Later kernel operations consume the fixed-file table, while the impact of shared-ring or delegated-interface use remains unknown. That concrete active-state chain requires review under the trust-boundary candidate rule, but it does not prove Important severity, host panic, or privilege escalation. 5. One-sentence report phrase A fault-and-reuse race lets an unprivileged io_uring process remove an unrelated replacement file from its active fixed-file table. 6. Manual review advice MANUAL CHECK REQUIRED Review shared-ring and delegated-ring consumers to determine whether wrong-file removal crosses a process or service trust boundary. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: io_uring/openclose: keep the lock in io_pipe_fixed() Commit: b4b7b2d19dab611f3cf3d052aa19278e7e4c4683 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b4b7b2d19dab611f3cf3d052aa19278e7e4c4683 Commit description: io_pipe_fixed() installs both ends of the pipe in the fixed file table, drops ->uring_lock, and copies the slot numbers to the application. If that faults, it takes the lock again and removes whatever is in these slots. If the request is run by io-wq the lock really is dropped in between, and the slots are visible to everybody else. By the time the error path gets to them, they may have been closed and reused, by IORING_OP_CLOSE and a direct open or accept, or by IORING_REGISTER_FILES_UPDATE. Then a file is removed from the table that has nothing to do with the failed request. Do the copy with the lock held. Faulting in user memory under ->uring_lock is fine, the registration paths do it all the time. Fixes: 53db8a7 ("io_uring: add support for IORING_OP_PIPE") Assisted-by: LLM Signed-off-by: Josef Bacik Link: https://patch.msgid.link/20261015-b4-io-uring-fixes-v1-38-c1556f5d7bf5@toxicpanda.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman Changed files: io_uring/openclose.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=b4b7b2d19dab611f3cf3d052aa19278e7e4c4683 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99265 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99265 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:L/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H The Best / paranoid CVSS score: 5.3 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: 4 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: MODERATE KPANIC detected for this report: YES Published priority for this report (same as in Subject): MODERATE 7.0 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).