From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72252][MODERATE 7.0] netfilter: nft_set_pipapo: don't leak bad clone into future transaction [ Upstream Date: Sat, 15 Aug 2026 18:58:10 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72252 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: 8 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: 047e813324eac2ac60cddfb58bcdbd0144eadb09 List-Id: CVE: CVE-2026-72252 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: netfilter: nft_set_pipapo: don't leak bad clone into future transaction [ Upstream Commit: 047e813324eac2ac60cddfb58bcdbd0144eadb09 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=047e813324eac2ac60cddfb58bcdbd0144eadb09 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72252 Analysis date: Sat, 15 Aug 2026 18:58:10 -0400 ActionableScore: 8 ActionableScore lower bound: 5 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A failed nft_set_pipapo insertion can leave a corrupted clone that may be reused by a later transaction and cause kernel out-of-bounds writes, requiring CAP_NET_ADMIN in typical deployments but potentially reachable by local users through delegated network namespaces. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72252 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72252 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-2026-72252 MODERATE 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-787;CWE-703;*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 failed nft_set_pipapo insertion can leave the cloned nft_pipapo_match object in a corrupted state after partial table resizing or scratch map changes. A later insertion in the same batch or in a future transaction can reuse that bad clone and trigger out-of-bounds writes in kernel memory. For the CVSS the PR:L is used because reliable triggering requires local ability to perform nf_tables control plane operations, commonly CAP_NET_ADMIN in a network namespace or delegated firewall management access. The issue is not directly network reachable because packet traffic alone does not trigger it. Impact is at least local denial of service via kernel memory corruption and in the paranoid case may include confidentiality and integrity impact or privilege escalation, so it should be manually reviewed.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) YES REMOTE WRITE OOB DANGER INIT NETFILTER HARDWARE LINUS KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=5 ## 1. ActionableScore * Conservative score: 5 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Memory corruption, strong corruption primitive: +2. The commit explicitly states that the next insertion can trigger out-of-bounds writes. * Privilege escalation plausible: +2. Kernel OOB writes in nf_tables control-plane state are a plausible LPE class, although no concrete exploit primitive is demonstrated. * Reliable kernel crash / strong DoS: +1. OOB writes in kernel memory can realistically crash the host. * Broad/default/common subsystem: +1. nf_tables is widely deployed, even though this is the control plane rather than packet RX/TX path. * Hard or unreliable condition: -1. Triggering depends on allocation failure and a later insertion using the bad clone. * Requires CAP_NET_ADMIN in typical deployments: -2. Direct nftables rule management usually requires CAP_NET_ADMIN. Paranoid additional interpretation: * Local unprivileged trigger: +1. In systems with unprivileged user namespaces and network namespaces, a local user may obtain CAP_NET_ADMIN inside a netns and reach nf_tables. * Local high-control netlink/control-plane API: +1. nf_tables gives detailed attacker control over set structure, batch ordering, keys, ranges, and transactional state. * Confidentiality impact plausible: +1. Kernel OOB write corruption can sometimes be shaped into disclosure or object corruption. * Integrity impact plausible: +1. OOB writes directly support integrity impact in kernel memory. * Capability penalty reduced in paranoid view: 0 instead of -2. Namespace delegation can make CAP_NET_ADMIN less equivalent to full host root. Call-site confidence: high. The patch shows the relevant insert failure path, clone state handling, abort behavior, and deactivate rejection path. ## 3. Reachability analysis The bug is triggered through nf_tables set updates using the pipapo set implementation. It is not directly network reachable because packet traffic alone does not create the bad clone or perform the transactional insertion sequence. In typical deployments, the attacker needs CAP_NET_ADMIN to update nftables rules, so the conservative interpretation treats this as a privileged local control-plane issue. However, on systems where unprivileged user namespaces are enabled and nf_tables is available inside network namespaces, a local unprivileged user may be able to create a namespace, obtain CAP_NET_ADMIN inside it, and exercise the affected path. Realistic triggering also requires a memory allocation failure during insertion, leaving a partially modified clone, followed by another insertion in the same batch or a later transaction. This makes exploitation harder than a direct OOB write, but the patch context explicitly confirms the OOB write consequence. ## 4. Severity interpretation This is not an ordinary Moderate correctness bug. The important factor is that the patch and commit message explicitly identify out-of-bounds writes after a failed insertion leaves a bad nft_pipapo_match clone. Realistic exploitation evidence is incomplete because the trigger depends on allocation failure and transactional sequencing, and no reclaim or controlled overwrite target is shown. Still, kernel OOB writes in nf_tables are historically high-risk and should not be auto-closed as a simple DoS. Overall this is Actionable Moderate at minimum and a Strong Important candidate under the namespace-enabled and paranoid interpretation. ## 5. One-sentence report phrase A failed nft_set_pipapo insertion can leave a corrupted clone that may be reused by a later transaction and cause kernel out-of-bounds writes, requiring CAP_NET_ADMIN in typical deployments but potentially reachable by local users through delegated network namespaces. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK. Reason: the patch explicitly describes kernel out-of-bounds writes in nf_tables transactional state, and namespace-dependent reachability can materially change the practical severity. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: nft_set_pipapo: don't leak bad clone into future transaction [ Upstream Commit: 047e813324eac2ac60cddfb58bcdbd0144eadb09 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=047e813324eac2ac60cddfb58bcdbd0144eadb09 Changed files: net/netfilter/nft_set_pipapo.c net/netfilter/nft_set_pipapo.h 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=047e813324eac2ac60cddfb58bcdbd0144eadb09 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72252 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72252 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: 5 Paranoid ActionableScore: 8 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).