From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98708][MODERATE 7.0] wifi: mac80211: keep paired old chanctx alive Date: Mon, 19 Oct 2026 02:21:49 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98708 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: 5 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 21a688cbeae0e682f03e91f1e7a7eedd60d9d4f2 List-Id: CVE: CVE-2026-98708 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: wifi: mac80211: keep paired old chanctx alive Commit: 21a688cbeae0e682f03e91f1e7a7eedd60d9d4f2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21a688cbeae0e682f03e91f1e7a7eedd60d9d4f2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98708 Analysis date: Mon, 19 Oct 2026 02:21:49 -0400 ActionableScore: 5 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: mac80211 can prematurely free an old paired channel context while a replacement context retains a stale reciprocal pointer, allowing later unreserve or switch-finalization processing to trigger an active-object use after free and possible kernel crash. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98708 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98708 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-2026-98708 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98708 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE_KPANIC RESULT=SAME (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:H/I:H/A:H';*CWE-416;CWE-415;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A lifetime management flaw in mac80211 can free an old WILL_BE_REPLACED channel context while its REPLACES_OTHER partner still retains a reciprocal replace_ctx pointer. A later unreserve or switch finalization path can follow this stale pointer and cause a use after free, with a possible repeated free of the old channel context depending on the later cleanup path. Impact is at least a local denial of service through kernel memory corruption and a kernel crash. In the worst still defensible case the stale kernel object may permit confidentiality and integrity impact or local privilege escalation, although a controllable write primitive is not proven by the supplied code. For the CVSS the PR:L reflects a local user or service with delegated wireless configuration capability rather than an unauthenticated remote attacker. AC:H reflects the required multi-vif in-place replacement and teardown sequence. The issue is not directly network reachable based on the supplied paths, and wireless traffic alone is not sufficient evidence of remote triggering. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 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 MODERATE_KPANIC to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because FD false positive review allowed a downgrade. 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 produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH. The independent weaker Aegis shadow evaluated CVSS 4.1 and ActionableScore 4 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. 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 5) MAYBE REMOTE DANGER INIT UAF KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 3 * Conservative score: 5 * Raw paranoid score: 3 * Paranoid score: 5 * Applied conservative floor: 3 -> 5 under REAL UAF FLOOR 5 because an active structured channel context is freed while an exact reciprocal reference survives and is later consumed by unreserve or switch-finalization processing. * Applied paranoid floor: 3 -> 5 for the same established lifetime mechanics. No speculative leverage bonus was added. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown Positive signals: * +2 Real UAF and lifetime violation. `ieee80211_free_chanctx()` can retire the old `WILL_BE_REPLACED` context while the paired `REPLACES_OTHER` context retains `replace_ctx` pointing to it. * +1 Realistic kernel crash or strong DoS. Later unreserve or switch-finalization processing dereferences the stale channel-context pointer and can fault or corrupt replacement state. Floor analysis: * The stale object is an active structured `ieee80211_chanctx`, not fixed stale storage. * The dangling pointer escapes the initial release path and remains part of an active reciprocal replacement relationship. * Later processing follows the stale pointer during pair teardown or switch finalization rather than being limited to an immediate destructor fault. * These mechanics preserve unresolved exploitation surface beyond a shallow invalid dereference, so FLOOR 5 is applied. Repeated-release analysis: * The first `ieee80211_free_chanctx()` can end the old context lifetime. * The exact pointer to the old context survives in the replacement partner. * A later stale dereference is established. * A concrete second `free`, `put`, or refcount mutation on that same already-freed context is not fully established by the supplied diff. * Concrete repeated release/refcount +1 was not awarded. * Paranoid repeated-refcount leverage +1 was withheld. * Structured stale-object leverage +1 was not separately awarded because attacker-controlled reclaim, replacement contents, or a distinct security-useful field consumption mechanism is not demonstrated. Material non-awarded signals: * Controlled reclaim or attacker-shaped replacement contents are not demonstrated. * Arbitrary or directed kernel write is not demonstrated. * Callback or function-pointer control is not demonstrated. * Confidentiality, integrity, and privilege-escalation points are not awarded from the UAF class alone. * Remote or adjacent-network triggering is not established. Wireless traffic alone does not prove reachability. * No race penalty was applied. The defect is an ordered lifetime error and the supplied evidence does not establish a narrow or unreliable timing window. * No host-admin penalty was applied because the complete privilege requirement is unresolved. * No extra Availability point was added for the same possible kernel crash. * B5-R, B3-PENDING, V32, V33, and B4-PENDING do not apply to this patch. Arithmetic: * Conservative: Real UAF +2, realistic kernel crash +1 = 3. FLOOR 5 changes 3 to 5. * Paranoid: Real UAF +2, realistic kernel crash +1 = 3. FLOOR 5 changes 3 to 5. * No hidden positive or negative points were applied. 3. Reachability analysis The vulnerable state arises during mac80211 multi-vif in-place channel-context replacement. Triggering requires creation of a replacement pair followed by release of the last assigned link or reassignment of that link to another existing context, after which an unreserve or switch-finalization path follows the surviving pointer. The supplied material does not establish whether an ordinary user, a delegated wireless-management service, a process with namespace-scoped `CAP_NET_ADMIN`, or only a host administrator can perform the complete sequence. Therefore `HostAdminRequired` and `NamespaceScopedPrivilege` remain `UNKNOWN`. The mere possibility of delegated wireless management is insufficient to prove below-host-admin reachability. No direct packet-triggered path is shown. A nearby wireless actor may influence operational events, but the evidence does not show that such an actor can independently create and tear down the required replacement state. No special hardware rarity penalty is applied because mac80211 hardware is common, although the affected multi-vif replacement configuration is more specific than ordinary Wi-Fi traffic. This is not shown to require a timing race. The invalid lifetime can result from an ordered state transition, so AC-like complexity comes from the required configuration and sequence rather than a proven narrow race window. 4. Primitive and severity interpretation The exact primitive is an active structured-object UAF. The old channel context may be freed while its replacement partner still contains an exact reciprocal pointer to it. Later pair teardown or switch-finalization code consumes that dangling pointer. This is stronger than fixed stale storage because the freed object remains represented as a live participant in a kernel state relationship. It is also stronger than an immediate cleanup-only fault because the stale reference survives into later processing. However, the supplied code does not establish controlled slab reclaim, attacker-selected replacement contents, arbitrary read or write, callback dispatch, or a completed local privilege-escalation chain. A concrete second lifetime mutation on the freed old context is not sufficiently visible. The newly added `ieee80211_free_chanctx(old_ctx)` occurs after the fixed code has preserved `old_ctx` until pairing teardown, so it does not by itself prove that vulnerable kernels performed a double free. The established primitive remains a stale post-lifetime dereference rather than a confirmed repeated-release primitive. `PrimitiveClass=CLASS_B` is appropriate. `ImportantCandidate=YES` reflects unresolved exploitation leverage from an escaping active-object UAF, not proof of Important severity. `AutoDowngradeAllowed=NO` is selected because automatically reducing this to an ordinary crash-only issue would discard the unresolved active-state lifetime primitive. Operationally, this is Actionable Moderate at minimum, with Important-vs-Moderate classification requiring inspection of the omitted finalization operations and actual privilege boundary. 5. One-sentence report phrase mac80211 can prematurely free an old paired channel context while a replacement context retains a stale reciprocal pointer, allowing later unreserve or switch-finalization processing to trigger an active-object use after free and possible kernel crash. 6. Manual review recommendation MANUAL CHECK REQUIRED Review the complete unreserve and switch-finalization call paths to determine whether the stale object is modified, freed again, or consumed through security-useful fields, and verify which local actor can perform the complete multi-vif replacement sequence. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: wifi: mac80211: keep paired old chanctx alive Commit: 21a688cbeae0e682f03e91f1e7a7eedd60d9d4f2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21a688cbeae0e682f03e91f1e7a7eedd60d9d4f2 Commit description: An in-place replacement keeps reciprocal replace_ctx pointers between the old WILL_BE_REPLACED chanctx and the new REPLACES_OTHER chanctx. However, the early free paths only consider assigned and reserved link users when deciding whether to free the old chanctx. That lets the old chanctx be freed too early while the replacement partner still points back to it, either when the last assigned link is released or when that link successfully reassigns to another existing context. Later unreserve and switch-finalization paths can then follow a stale replace_ctx pointer. Keep a paired old chanctx alive until the replacement pair has been torn down. Apply the same check to both __ieee80211_link_release_channel() and ieee80211_link_use_reserved_reassign(). If the replacement is later abandoned, ieee80211_link_unreserve_chanctx() already tears down the pairing before freeing the old chanctx once no users remain. Fixes: 5bcae31 ("mac80211: implement multi-vif in-place reservations") Cc: stable@vger.kernel.org Reported-by: Vega Signed-off-by: Zhiling Zou Link: https://patch.msgid.link/b9b582b0db3814f641648b8886bb50f9d68f93ac.1785730815.git.zhilinz@nebusec.ai Signed-off-by: Johannes Berg Signed-off-by: Greg Kroah-Hartman Changed files: net/mac80211/chan.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=21a688cbeae0e682f03e91f1e7a7eedd60d9d4f2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98708 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98708 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:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 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: 5 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).