From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99267][LOW] io_uring/napi: make stale entries time out after 60s Date: Tue, 03 Nov 2026 22:53:46 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99267 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: 3fe820cf35f83534eab72ea73f1a83cfd3cd8079 List-Id: CVE: CVE-2026-99267 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: io_uring/napi: make stale entries time out after 60s Commit: 3fe820cf35f83534eab72ea73f1a83cfd3cd8079 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3fe820cf35f83534eab72ea73f1a83cfd3cd8079 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99267 Analysis date: Tue, 03 Nov 2026 22:53:46 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: An incorrect io_uring NAPI timeout retains stale IDs for years and repeatedly polls them, permitting local CPU-overhead growth without shown memory corruption or security-boundary bypass. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99267 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99267 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-2026-99267 LOW https://www.kernelcve.org/list/?q=CVE-2026-99267 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-682;**CWE-400;*CWE-772;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'An incorrect timeout calculation causes dynamically tracked NAPI entries to remain associated with an io_uring instance for years instead of being removed after 60 seconds. Every retained NAPI ID can then be busy polled on later waits, allowing CPU overhead to grow when a local process repeatedly creates sockets or changes the NAPI IDs observed by the ring. The demonstrated primitive is stale entry retention and repeated polling, not UAF, OOB access, information disclosure, or memory corruption. For the CVSS the PR:L value reflects that an attacker needs local user or process access to configure and use the affected io_uring NAPI path. Remote traffic alone is not shown to create or operate the vulnerable ring. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. 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 CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to LOW because the ActionableScore threshold 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 INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE SIMPLEFIX LEAK IO_URING INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=NONE 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: 2. * Conservative score: 2; no floor or cap applied. * Raw paranoid score: 2. * Paranoid score: 2; growing polling overhead does not establish a distinct host-wide DoS. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Local unprivileged trigger: supplied evidence grounds local process access to configure and exercise the io_uring NAPI path. * +1 Concrete persistent kernel resource retention: the incorrect timeout effectively retains dynamically tracked NAPI entries for years, causing continued polling. * No crash/strong-DoS point: increasing CPU overhead is plausible, but reliable host-wide exhaustion, panic, or persistent system unavailability is not shown. * No corruption point: the patch changes only timeout arithmetic; no OOB access, UAF, stale memory dereference, or write primitive is evidenced. * NEW52/B5-R does not apply: there is no retry-accumulated heap OOB write or corrupted descriptor consumption. * No authorization, shared-backing, confidentiality, or integrity signal is shown. 3. Reachability analysis A local non-host-admin process can create and use the affected io_uring/NAPI state and accumulate IDs through socket activity. Remote traffic alone cannot create or operate the ring. No host UID 0, host capability, special hardware, prior privileged setup, or race is evidenced. Namespace capability scope is irrelevant to the shown path and remains unresolved. 4. Primitive and severity reading The defect is an arithmetic error that prevents timely expiry of valid NAPI tracking entries. Those entries remain actively polled, but they are not shown to reference freed memory or corrupt structured state. The demonstrated consequence is resource retention and increasing CPU work, not a memory-corruption or authorization primitive. Therefore PrimitiveClass is NONE, ImportantCandidate is NO, and automatic downgrade is allowed. 5. One-sentence report phrase An incorrect io_uring NAPI timeout retains stale IDs for years and repeatedly polls them, permitting local CPU-overhead growth without shown memory corruption or security-boundary bypass. 6. Manual review advice NO MANUAL CHECK NEEDED The patch and supplied evidence establish only bounded resource-retention/CPU-overhead behavior. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: io_uring/napi: make stale entries time out after 60s Commit: 3fe820cf35f83534eab72ea73f1a83cfd3cd8079 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3fe820cf35f83534eab72ea73f1a83cfd3cd8079 Commit description: With dynamic tracking a NAPI id that hasn't been seen for a minute is meant to be dropped from the list the ring busy polls. The timeout is added to jiffies, but it is defined as 60 * SEC_CONVERSION, and SEC_CONVERSION isn't the number of jiffies in a second. It is the internal factor of __timespec64_to_jiffies(), HZ scaled up by SEC_JIFFIE_SC bits. For HZ=1000 that is 1000 << 22, which puts the timeout at about eight years. On 32-bit the multiplication overflows. So entries are never removed, and every id that a socket of the ring ever had keeps being polled on each wait. Fixes: 8d0c12a ("io-uring: add napi busy poll support") Assisted-by: LLM Signed-off-by: Josef Bacik Link: https://patch.msgid.link/20261015-b4-io-uring-fixes-v1-33-c1556f5d7bf5@toxicpanda.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman Changed files: io_uring/napi.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=3fe820cf35f83534eab72ea73f1a83cfd3cd8079 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99267 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99267 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:L/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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).