From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98790][LOW] perf: Fix race between perf_event_exit_task() and perf_pending_task() [ Upstream Date: Fri, 23 Oct 2026 19:44:01 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98790 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: 1 X-AL-KERNEL-Commit: 672b8a9ce8f51b991481dfde26fba5cc4340a91a List-Id: CVE: CVE-2026-98790 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: perf: Fix race between perf_event_exit_task() and perf_pending_task() [ Upstream Commit: 672b8a9ce8f51b991481dfde26fba5cc4340a91a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=672b8a9ce8f51b991481dfde26fba5cc4340a91a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98790 Analysis date: Fri, 23 Oct 2026 19:44:01 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A local process can race perf event cleanup with pending SIGTRAP handling during exec, causing an invalid context warning and a conditional kernel panic on systems using panic_on_warn, without evidence of UAF, memory corruption, information disclosure, or authorization bypass. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98790 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98790 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-2026-98790 LOW https://www.kernelcve.org/list/?q=CVE-2026-98790 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT LOW AEGIS_AS=0 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:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-667;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 race between perf_event_exit_task and pending perf SIGTRAP processing can occur during begin_new_exec. perf_event_exit_task can replace ctx task with TASK_TOMBSTONE while perf_pending_task continues into perf_sigtrap because PF_EXITING is not necessarily set during exec. The demonstrated result is WARN_ON_ONCE after the event context no longer belongs to current. No UAF, OOB access, information leak, or write primitive is established by the supplied code because TASK_TOMBSTONE is used as a state marker rather than a freed task pointer. For the CVSS the PR:L value is selected because a local user process must create and control a permitted perf event and execute the affected transition. AC:H is selected because successful triggering depends on winning a race window between pending perf processing and exec cleanup. The issue is not network reachable. Impact is normally limited to incorrect event handling and a kernel warning, but systems configured with panic_on_warn may experience a kernel crash and denial of service. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 4.7 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 MODERATE to LOW because the CVSS score, vector or bug class 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 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class NONE 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 INIT SIMPLEFIX RACE HARDWARE DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 2 * Paranoid score: 2 * No floor or cap applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 conservative and paranoid: local unprivileged trigger. A process can create a permitted self-targeted perf event with SIGTRAP behavior and execute the affected exec transition without host-administrator privileges. * +1 paranoid only: conditional kernel crash. The demonstrated WARN_ON_ONCE can become fatal on systems configured with panic_on_warn. * +0 for the race itself. No timing penalty is applied because the supplied evidence does not establish that the race is one-shot, exceptionally narrow, or impractical to retry. * No UAF, OOB access, arbitrary write, refcount mutation, controlled reclaim, information disclosure, or authorization bypass is established. * No additional availability point is awarded because a panic caused by panic_on_warn is the same conditional crash consequence. * No C or I signal is awarded. TASK_TOMBSTONE is a state marker, and the shown path establishes an invalid-state warning rather than post-lifetime object use. * NEW52 B5-R does not apply because there is no heap OOB write or retry-accumulated offset. * NEW53 B3-PENDING does not apply because no shared-backing write exists. * NEW54 B4-PENDING does not apply because no DENY-to-ALLOW authorization decision changes. 3. Reachability analysis The evaluated attacker is an ordinary local process operating on its own perf event and task lifecycle. Host UID 0 and host-admin-equivalent capabilities are not inherently required for a permitted self-monitoring perf event, although perf_event_paranoid and product policy can restrict availability. No namespace capability is required or material to the trigger. No network path, special hardware, delegated control plane, or prior privileged setup is established. The process can retry event creation and exec transitions, but the exact scheduling interleaving remains timing-dependent. 4. Primitive and severity interpretation The exact defect is a race-driven state-validation failure. perf_event_exit_task sets ctx task to TASK_TOMBSTONE during exec, while pending SIGTRAP processing can continue because PF_EXITING is not set. The stale logical state reaches WARN_ON_ONCE. This is CLASS_C invalid-state behavior, not a lifetime violation. The context pointer is not shown to be freed, the sentinel is intentionally assigned, and no operation through reclaimed storage is demonstrated. The established consequence is a kernel warning. A kernel panic is conditional on panic_on_warn. ImportantCandidate is NO because there is no corruption, security-boundary bypass, active-state replacement primitive, or exploitation leverage beyond the warning or conditional crash. AutoDowngradeAllowed is YES because no unresolved Important-preserving primitive remains. 5. One-sentence report phrase A local process can race perf event cleanup with pending SIGTRAP handling during exec, causing an invalid context warning and a conditional kernel panic on systems using panic_on_warn, without evidence of UAF, memory corruption, information disclosure, or authorization bypass. 6. Manual review recommendation NO MANUAL CHECK NEEDED The supplied patch establishes a WARN-only state race with no independent corruption or security-boundary primitive. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: perf: Fix race between perf_event_exit_task() and perf_pending_task() [ Upstream Commit: 672b8a9ce8f51b991481dfde26fba5cc4340a91a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=672b8a9ce8f51b991481dfde26fba5cc4340a91a Changed files: kernel/events/core.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=672b8a9ce8f51b991481dfde26fba5cc4340a91a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98790 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98790 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: 1 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).