From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-97608][MODERATE 7.0] netfilter: nf_log: unregister loggers before per-net teardown Date: Tue, 29 Sep 2026 10:11:47 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-97608 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: 4 X-AL-KERNEL-Commit: eaec35fae8f2052c1878a5c7cc7699d8357d79f2 List-Id: CVE: CVE-2026-97608 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: netfilter: nf_log: unregister loggers before per-net teardown Commit: eaec35fae8f2052c1878a5c7cc7699d8357d79f2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eaec35fae8f2052c1878a5c7cc7699d8357d79f2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97608 Analysis date: Tue, 29 Sep 2026 10:11:47 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97608 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97608 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-2026-97608 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97608 CHECK WITH IMPACT FROM ORIG NN MODERATE 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-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race during nf_log_syslog or nfnetlink_log teardown can leave a stale per network logger pointer after the global backend and its module memory have been released. A sysctl or netlink writer can rebind the logger after the per network pre exit callback clears it but before nf_log_unregister removes the global registration. A later sysctl read or packet logging operation can dereference the freed backend and cause a kernel crash. The confirmed impact is at least local denial of service. Because the stale object contains logger backend data and callbacks, the worst case may include confidentiality and integrity impact if the freed target can be reused or influenced. For the CVSS the PR:L value is used for the paranoid score because a process with delegated CAP_NET_ADMIN, container root, or equivalent netfilter control may race module teardown performed by an administrator or system service. AC:H applies because successful triggering depends on a narrow timing window during module removal. The issue is not directly remotely reachable because network traffic alone cannot create the stale pointer, although packet logging can dereference it after the race has occurred.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE REMOTE INIT NETFILTER RACE LOG HARDWARE KPANIC PACKET KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 3 * Conservative score: 4 * Raw paranoid score: 4 * Paranoid score: 5 * Applied conservative FLOOR 4: 3 -> 4 because a stale active logger backend is used after module memory is freed, and host-admin-equivalent attacker privilege is not established. * Applied paranoid FLOOR 5: 4 -> 5 because the pointer escapes teardown into later active packet-logging or sysctl processing, where logger backend data or callbacks can be consumed. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown Conservative signals: * +2 Real UAF. A per-network logger pointer can remain after the logger backend and containing module memory have been freed. * +1 Concrete RCU lifetime mismatch. Teardown ordering permits the per-network reference to be republished after it is cleared, defeating the grace-period-based lifetime protocol. * +1 Reliable kernel crash or strong DoS. A later sysctl read or packet-logging operation can dereference freed module memory. * -1 Hard one-shot teardown race. Triggering requires rebinding during a narrow module-exit window. Raw conservative score: 2 + 1 + 1 - 1 = 3. Additional paranoid signal: * +1 Structured stale-object leverage. The stale reference escapes teardown and can reach active logger processing that consumes backend state or callbacks. The writer influences which registered logger is rebound, although reclaimed contents are not shown to be controlled. Raw paranoid score: 2 + 1 + 1 + 1 - 1 = 4. Not awarded: * Controlled reclaim or attacker-shaped replacement contents are not demonstrated. * Arbitrary kernel read or write is not demonstrated. * Strong callback hijacking is not established because control over reclaimed module memory is not shown. * Confidentiality and integrity points are not awarded from the theoretical UAF consequences. * Remote reachability is not established. Packets can perform the later dereference but cannot independently create the stale pointer. * Local unprivileged trigger is not awarded because the complete module-unload and writer sequence is unresolved. * Repeatable lifetime manipulation is not awarded because module unloading and logger rebinding may be controlled by different security principals. * No concrete repeated release or refcount mutation exists. There is no first release followed by a second put or release through the exact dangling reference. * No additional Availability point is awarded for the same kernel crash. 3. Reachability analysis The trigger is compound. One path unloads `nf_log_syslog` or `nfnetlink_log`, while a concurrent sysctl or netlink writer rebinds the still-registered logger during per-network teardown. A later sysctl read or packet-logging operation performs the stale access. Module unloading is ordinarily performed by a host administrator or privileged service. The supplied evidence does not establish that the attacker must personally possess that privilege, because a lower-privileged writer could potentially race an independently initiated module unload. Therefore, `HostAdminRequired=UNKNOWN` rather than YES or NO. The logger selection is per-network namespace, but the complete trigger also includes global backend removal and module unloading. The evidence does not establish that every required stage is available within an attacker-created user or network namespace. Therefore, `NamespaceScopedPrivilege=UNKNOWN`. This is not directly remotely triggerable. Network traffic may cause the final packet-logging dereference after the stale pointer exists, but traffic alone cannot perform the required teardown and rebinding sequence. No special hardware or boot option is indicated. The timing window is narrow and tied to module exit, so the race penalty is supported. 4. Primitive and severity interpretation The exact primitive is a stale post-lifetime pointer from `net->nf.nf_loggers[pf]` into a logger backend residing in freed module memory. This is a real UAF involving an active structured object, not fixed stale storage. The defect originates during teardown, but the stale reference survives teardown and can later be consumed by ordinary sysctl or packet-logging processing. It is therefore broader than an immediate cleanup-only fault. No double release or second refcount mutation is present. This is CLASS_B rather than CLASS_A. Active backend state and potentially a callback can be reached through the stale pointer, but controlled reclaim, attacker-controlled replacement contents, directed memory access, or demonstrated callback control is absent. The demonstrated consequence is kernel crash or DoS. A stronger consequence is technically conceivable if freed module memory can be reused or influenced before the stale callback or metadata access, but that mechanism is not established by the supplied evidence. `ImportantCandidate=YES` because an active logger pointer escapes module lifetime and reaches later structured processing, leaving meaningful exploitation leverage unresolved. `AutoDowngradeAllowed=NO` because automatically treating this as an ordinary teardown crash could discard the unresolved callback-bearing UAF primitive. The likely operational severity is Actionable Moderate, with Important classification dependent on manual confirmation of the stale-use call sites and module-memory reuse behavior. 5. One-sentence report phrase A teardown race can leave a per-network nf_log pointer referencing freed module backend memory, allowing a later sysctl read or packet-logging operation to trigger a host kernel UAF and crash, with callback-related exploitation leverage requiring manual review. 6. Manual review recommendation MANUAL CHECK REQUIRED Review the exact sysctl and packet-logging dereferences, whether a stale logger callback can be invoked after module memory release, and whether module-address reuse can provide influence beyond an immediate fault. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: nf_log: unregister loggers before per-net teardown Commit: eaec35fae8f2052c1878a5c7cc7699d8357d79f2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eaec35fae8f2052c1878a5c7cc7699d8357d79f2 Commit description: nf_log_syslog and nfnetlink_log unregister their per-network namespace operations before unregistering their global logger backends. This leaves a window where a sysctl or netlink writer can rebind the still- registered logger after the per-net pre-exit callback cleared the old selection. The race looks like this: CPU 0 CPU 1 ---- ---- unregister_pernet_subsys() nf_log_unset(net, logger) net->nf.nf_loggers[pf] = NULL lock nf_log_mutex find logger in loggers[][] net->nf.nf_loggers[pf] = logger unlock nf_log_mutex nf_log_unregister(logger) lock nf_log_mutex loggers[pf][type] = NULL unlock nf_log_mutex synchronize_rcu() module exit returns module core frees backend memory Later, a sysctl read or packet logging operation can dereference the stale per-net logger pointer. Fix this by unregistering the global logger backends before tearing down per-net state. Once the global registrations are gone, later writers can no longer rebind the logger. unregister_pernet_subsys() already waits for an RCU grace period after the pre-exit callback clears the per-net selection, while nf_log_unregister() continues to cover readers of the global logger table. Apply this ordering fix to both nf_log backends that combine per-net teardown with global logger registration. Fixes: 5b023fc ("netfilter: enable per netns support for nf_loggers") Cc: stable@vger.kernel.org Signed-off-by: Chengfeng Ye Signed-off-by: Pablo Neira Ayuso Signed-off-by: Greg Kroah-Hartman Changed files: net/netfilter/nf_log_syslog.c net/netfilter/nfnetlink_log.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=eaec35fae8f2052c1878a5c7cc7699d8357d79f2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97608 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97608 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:H/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: 4 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).