From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99230][LOW] io_uring/cmd: don't leave list poison in ->hash_node Date: Mon, 02 Nov 2026 23:18:05 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99230 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: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: cc7f13d006fcefed9564bd79f135b51d344e9c77 List-Id: CVE: CVE-2026-99230 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: io_uring/cmd: don't leave list poison in ->hash_node Commit: cc7f13d006fcefed9564bd79f135b51d344e9c77 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc7f13d006fcefed9564bd79f135b51d344e9c77 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99230 Analysis date: Mon, 02 Nov 2026 23:18:05 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A timing-dependent io_uring request-reuse bug leaves a poisoned hlist node that later causes a fixed invalid-address write attempt and kernel fault. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99230 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99230 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-2026-99230 LOW https://www.kernelcve.org/list/?q=CVE-2026-99230 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: LOW, Aegis: 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:N/A:H';CWE-665;CWE-824;CWE-362;BEST CVSS score: '4.7';DESCR 'An io_uring request recycled after a cancelable uring_cmd such as ublk FETCH_REQ can retain LIST_POISON1 and LIST_POISON2 in hash_node because io_uring_cmd_del_cancelable used hlist_del rather than hlist_del_init. During a vectored futex wake race, io_futexv_complete can call hlist_del_init on that recycled node and attempt a write through fixed LIST_POISON2, causing a general protection fault and kernel crash. For the CVSS the PR:L value is selected because a local process must use io_uring and reach an affected cancelable uring_cmd consumer before triggering the futexv completion path. AC:H reflects the required request reuse and wake timing. The demonstrated primitive is a write through a fixed invalid poison address, not an attacker controlled write or a proven UAF, so C:N and I:N are retained while A:H reflects host kernel failure. The issue is not directly network reachable. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 0 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 KP specialist did not establish a qualifying panic and 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 KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE KASAN OOB INIT LEAK IO_URING KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 0. * Conservative score: 0; no floor or cap applied. * Raw paranoid score: 0. * Paranoid score: 0; no additional technically supported primitive. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Reliable kernel crash: recycled `hash_node` retains poison, and later `hlist_del_init()` attempts a write through fixed `LIST_POISON2`, producing the documented general-protection fault. * -1 Hard timing/reuse requirement: triggering requires request-cache reuse across different request roles plus a futex wake while `futex_wait_multiple_setup()` is still queueing. * No overwrite bonus: the supplied trace shows an attempted access to a non-canonical poison address that faults, not a confirmed write landing in kernel memory. * No UAF: the request is deliberately recycled; the defect is failure to reinitialize embedded list state, not use after object lifetime. * No controlled target, payload, reclaim, callback influence, confidentiality, integrity, authorization bypass, or second availability effect is shown. * B5-R does not apply: there is no retry-accumulated heap OOB write or later consumption of corrupted heap state. 3. Reachability analysis A local process must exercise io_uring, an affected cancelable `uring_cmd` consumer such as ublk, request reuse, and the vectored-futex wake ordering. The summary labels this PR:L, but the patch does not establish the permissions or provisioning needed for the complete ublk/cancelable-command stage. Therefore host-admin and namespace-scoped reachability remain unknown, and no local-unprivileged bonus or privilege penalty is applied. There is no remote path or special hardware requirement shown. 4. Primitive and severity reading The exact primitive is stale poison metadata in a recycled active request, followed by an `hlist_del_init()` write attempt through a fixed non-canonical poison pointer. This is CLASS_C invalid-state/crash behavior rather than a confirmed heap overwrite, UAF, or useful write primitive. The shown effect is a kernel Oops/host denial of service; useful corruption past the fault is unsupported. ImportantCandidate is NO and automatic downgrade is allowed because the fixed poison address predictably faults and no material non-crash leverage remains unknown. 5. One-sentence report phrase A timing-dependent io_uring request-reuse bug leaves a poisoned hlist node that later causes a fixed invalid-address write attempt and kernel fault. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm the complete permissions and setup required for the affected cancelable `uring_cmd` consumer; the primitive itself remains crash-only on supplied evidence. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: io_uring/cmd: don't leave list poison in ->hash_node Commit: cc7f13d006fcefed9564bd79f135b51d344e9c77 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc7f13d006fcefed9564bd79f135b51d344e9c77 Commit description: io_uring_cmd_del_cancelable() uses hlist_del() to take a command off ->cancelable_uring_cmd, which leaves LIST_POISON1/2 behind in ->hash_node. Requests are recycled through the request cache without being reinitialised, and not every user of ->hash_node sets it up before it is used: If a vectored futex wait is woken while futex_wait_multiple_setup() is still queueing the futexes, io_futexv_wait() doesn't add the request to ->futex_list, and leaves the completion to the task_work queued by the wake up. io_futexv_complete() ends in __io_futex_complete(), whose hlist_del_init() is fine for a request that is unhashed, which is how all other users of the node leave it. If the request was a cancelable uring_cmd in its previous life, e.g. a ublk FETCH_REQ, it writes through LIST_POISON2: Oops: general protection fault, probably for non-canonical address KASAN: maybe wild-memory-access in range [0xdead000000000120-...] RIP: 0010:io_futexv_complete+0x219/0x420 Call Trace: tctx_task_work_run+0x804/0x950 tctx_task_work+0x71/0xa0 task_work_run+0x118/0x200 Leave the node unhashed. Fixes: 93b8cc6 ("io_uring: cancelable uring_cmd") Assisted-by: LLM Signed-off-by: Josef Bacik Link: https://patch.msgid.link/20261015-b4-io-uring-fixes-v1-2-c1556f5d7bf5@toxicpanda.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman Changed files: io_uring/uring_cmd.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=cc7f13d006fcefed9564bd79f135b51d344e9c77 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99230 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99230 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: Not available 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: 0 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).