From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45897][LOW] netfilter: nft_counter: serialize reset with spinlock [ Upstream Date: Wed, 27 May 2026 22:36:24 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45897 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: 0 X-AL-KERNEL-Commit: 0cdc6d5a26f2d1f7f15a43526841b679445c32e2 List-Id: CVE: CVE-2026-45897 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: netfilter: nft_counter: serialize reset with spinlock [ Upstream Commit: 0cdc6d5a26f2d1f7f15a43526841b679445c32e2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0cdc6d5a26f2d1f7f15a43526841b679445c32e2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45897 Analysis date: Wed, 27 May 2026 22:36:24 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: Concurrent nftables counter dump-and-reset operations can double subtract the same values, causing local counter accounting underflow without memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45897 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45897 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-2026-45897 LOW CHECK 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:L/A:L';CWE-362;CWE-667;CWE-682;CWE-191;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '4.4';DESCR 'nft_counter dump and reset operations were not serialized, so two concurrent reset requests could read the same counter values and both subtract them. This can underflow or corrupt nftables counter accounting and make firewall statistics unreliable. For the CVSS the PR:L is used in the paranoid score because delegated CAP_NET_ADMIN in containers or service accounts can expose nftables control plane operations below full host root, while normal host triggering requires network administration privileges. The issue is not network reachable and is triggered through local netfilter configuration operations rather than packet traffic. Impact is limited to counter integrity and possible low availability impact in management workflows. No supported evidence indicates information disclosure, kernel memory corruption, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) MAYBE REMOTE LOCK SIMPLEFIX NETFILTER HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown * Integrity impact plausible: +1 Concurrent reset can corrupt nftables counter accounting by double subtracting the same fetched values. * Local delegated network administration trigger: +1 in paranoid scoring Delegated `CAP_NET_ADMIN` in containers or service accounts may expose nftables counter reset operations below full host root. * Requires CAP_NET_ADMIN in typical deployments: -2 conservative nftables object/rule/set counter reset operations are normally local firewall control-plane operations requiring network administration privileges. * No availability impact in conservative scoring: +0 This is primarily counter/statistics underflow, not a crash, hang, memory leak, or packet-processing outage. * No memory corruption: +0 The issue is race-based accounting inconsistency, not UAF, OOB write, arbitrary write, or object lifetime corruption. * No remote reachability: +0 Packet traffic updates counters, but the vulnerable operation is local concurrent dump-and-reset through netfilter control plane. ## 3. Reachability analysis A local actor with nftables administration rights can trigger the issue by issuing concurrent counter dump-and-reset operations. In normal host deployments this requires `CAP_NET_ADMIN`. In namespaces or containerized systems, delegated network administration may allow a less privileged tenant or service account to affect counters in its namespace. The issue is not remotely triggerable by network packets alone. Realistic exploitation is limited to inaccurate counter values or management/statistics disruption. ## 4. Severity interpretation This behaves like Low or ordinary Moderate. It affects accounting integrity, but does not compromise packet filtering decisions, does not corrupt kernel memory, and does not provide privilege escalation or information disclosure. The main risk is unreliable firewall statistics after concurrent reset operations. ## 5. One-sentence report phrase Concurrent nftables counter dump-and-reset operations can double subtract the same values, causing local counter accounting underflow without memory corruption or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is a local `CAP_NET_ADMIN` accounting race with no memory corruption, no remote reachability, and no demonstrated security-boundary bypass. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: nft_counter: serialize reset with spinlock [ Upstream Commit: 0cdc6d5a26f2d1f7f15a43526841b679445c32e2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0cdc6d5a26f2d1f7f15a43526841b679445c32e2 Changed files: net/netfilter/nft_counter.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=0cdc6d5a26f2d1f7f15a43526841b679445c32e2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45897 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45897 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:H/UI:N/S:U/C:N/I:L/A:N The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L The Best / paranoid CVSS score: 4.4 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: 0 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).