From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99058][LOW] workqueue: Fix NULL current_pwq deref in chained work check Date: Mon, 26 Oct 2026 20:29:22 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99058 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: 3dc61af2998cfc7312d6e59bbdcd5eed074483f2 List-Id: CVE: CVE-2026-99058 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: workqueue: Fix NULL current_pwq deref in chained work check Commit: 3dc61af2998cfc7312d6e59bbdcd5eed074483f2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3dc61af2998cfc7312d6e59bbdcd5eed074483f2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99058 Analysis date: Mon, 26 Oct 2026 20:29:22 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A kworker can dereference a NULL `current_pwq` while queueing onto a draining or destroying workqueue, causing a possible kernel Oops or panic without evidence of memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99058 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99058 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-2026-99058 LOW https://www.kernelcve.org/list/?q=CVE-2026-99058 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 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-476;CWE-754;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 NULL pointer dereference can occur in is_chained_work because current_wq_worker may return a kworker whose current_pwq is NULL when it is not executing a work item. Triggering requires the unusual state where such a kworker queues work while the target workqueue is draining or being destroyed, so attack complexity is high and direct network reachability is not established. For the CVSS the PR:L value reflects that a local user or process would need to influence a subsystem that reaches this internal workqueue path, while direct control of the required kworker state is not demonstrated. The proven primitive is a NULL pointer read that can cause an oops and may cause a system panic depending on kernel configuration. There is no evidence of UAF, OOB access, information disclosure, controlled write, or privilege escalation. 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 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 1 with primitive class CLASS_C 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 1) MAYBE LOCK WARNONLY SIMPLEFIX LINUS TEST KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 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: 1. * Conservative score: 1; no floor or cap applied. * Raw paranoid score: 1. * Paranoid score: 1; no additional technically supported primitive. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Reliable kernel crash / strong DoS: `worker->current_pwq` can be NULL, and the old expression dereferences it before reaching the intended warning, plausibly causing an Oops or panic. * +0 Weak corrupt concern: this is a NULL-pointer read/dereference, not a write or persistent state corruption. * No timing penalty: draining or destruction is required, but the evidence does not establish a narrow, attacker-uncontrollable race. * No local-unprivileged bonus: no attacker-accessible caller or complete trigger is shown. * No UAF, OOB access, controlled write, disclosure, authorization bypass, or privilege escalation is shown. * No extra availability point: a panic would be the same fault already counted. 3. Reachability analysis The vulnerable state requires a kworker that is not executing a work item to queue work against a draining or destroying workqueue. The patch establishes this internal state but does not identify an attacker-invocable subsystem path or who controls workqueue teardown and queueing. Local low-privilege reachability in the legacy hint is conjectural rather than demonstrated. Host-admin, UID 0, namespace capability, prior setup, hardware, and repeatability requirements therefore remain unresolved. 4. Primitive and severity reading The exact primitive is a NULL `current_pwq` dereference in `is_chained_work()`. It is neither stale storage nor an active-object lifetime violation. The supported consequence is an immediate kernel fault; no useful non-crash primitive remains. This is CLASS_C, not B5-R, B3-PENDING, or B4-PENDING. ImportantCandidate is NO because no corruption or security-boundary mechanism is shown. Auto-downgrade is allowed, while manual review remains advisable to resolve actual caller reachability and operational crash exposure. 5. One-sentence report phrase A kworker can dereference a NULL `current_pwq` while queueing onto a draining or destroying workqueue, causing a possible kernel Oops or panic without evidence of memory corruption or privilege escalation. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm which subsystems can create the required state and whether an unprivileged actor can induce the complete sequence. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: workqueue: Fix NULL current_pwq deref in chained work check Commit: 3dc61af2998cfc7312d6e59bbdcd5eed074483f2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3dc61af2998cfc7312d6e59bbdcd5eed074483f2 Commit description: current_wq_worker() only tells us that %current is a kworker. It does not guarantee that the worker is currently executing a work item, as worker->current_pwq is populated only while process_one_work() is running the work function. is_chained_work() can be reached while queueing on a draining or destroying workqueue. If a kworker outside work-item execution reaches that path, current_wq_worker() returns a worker but worker->current_pwq is NULL, and the chained-work test can fault before it emits the intended warning. Guard the chained-work test with worker->current_pwq. A kworker without current_pwq is not executing work on the target workqueue, so the helper should return false and let the draining/destroying warning fire. Fixes: 8d03ecf ("workqueue: reimplement is_chained_work() using current_wq_worker()") Cc: stable@vger.kernel.org Signed-off-by: Pavankumar Kondeti Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman Changed files: kernel/workqueue.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=3dc61af2998cfc7312d6e59bbdcd5eed074483f2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99058 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99058 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).