From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-52999][MODERATE 7.0] netfilter: nfnetlink_osf: fix out-of-bounds read on option matching [ Upstream Date: Wed, 24 Jun 2026 13:35:16 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-52999 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 0145548346c4a30981a870a8ca00eac46ba27e85 List-Id: CVE: CVE-2026-52999 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: netfilter: nfnetlink_osf: fix out-of-bounds read on option matching [ Upstream Commit: 0145548346c4a30981a870a8ca00eac46ba27e85 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0145548346c4a30981a870a8ca00eac46ba27e85 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52999 Analysis date: Wed, 24 Jun 2026 13:35:16 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A remote TCP packet can trigger an out-of-bounds read in nfnetlink_osf option matching when OSF all-match logging is configured, causing incorrect fingerprint results and possible DoS, but no write primitive or privilege escalation path is shown. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52999 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52999 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-2026-52999 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';CWE-125;*CWE-20;CWE-754;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '7';DESCR 'An out-of-bounds read in nfnetlink_osf can occur because nf_osf_match_one advanced the shared ctx optp pointer while parsing TCP options and did not restore it after a successful fingerprint match. If NF_OSF_LOGLEVEL_ALL is configured, the caller may continue checking later fingerprints with optp already positioned at the end of the TCP options buffer, so the next match can read garbage or data outside the expected option area. A remote host can trigger the affected parsing path by sending crafted TCP packets to a system that uses netfilter OSF fingerprint matching with all-match logging enabled. For the CVSS the PR:N value is used because the attacker only needs network reachability to the filtered interface once the vulnerable OSF rule is present. The issue is network reachable but depends on a non-default firewall configuration, so AC:H is used. Impact is mainly incorrect matching or logging and possible denial of service from an invalid read. In the paranoid score, limited confidentiality and integrity impact are kept for manual-review sensitivity, but the class remains out-of-bounds read rather than memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES REMOTE OOB INIT NETFILTER DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Remote reachable / network-triggerable: +2 A remote TCP packet can reach the OSF matching path if the target system has netfilter OS fingerprint matching configured. * Integrity impact plausible: +1 The bug can cause incorrect OS fingerprint matching or incorrect logging behavior. * Common networking / packet-processing path: +1 The vulnerable code runs from the netfilter packet-processing path, although the specific OSF matcher is not commonly enabled. * Non-default runtime configuration: -1 Triggering requires configured nfnetlink_osf rules and specifically NF_OSF_LOGLEVEL_ALL behavior for repeated fingerprint checks. Conservative total: 3 Paranoid additional signals: * Weak / indirect corruption candidate: +1 The patch title and behavior indicate an out-of-bounds read, but only a read primitive is shown. There is no write, UAF, double-free, callback corruption, or object replacement primitive. * Availability impact plausible: +1 An invalid read in a kernel packet path may plausibly cause a fault or unstable behavior, but the commit mainly describes garbage reads and incorrect matches rather than a demonstrated reliable crash. Paranoid total: 5 No strong memory corruption signal is awarded because the patch shows a read-only pointer traversal bug, not OOB write, UAF, double-free, type confusion, or controlled overwrite. ## 3. Reachability analysis The bug is reachable by remote TCP packets only when the host has nfnetlink_osf fingerprint matching rules installed and uses the all-match logging mode that continues checking fingerprints after a successful match. The attacker does not need local privileges on the victim once this firewall configuration exists. For CVSS-style PR, this corresponds to PR:N from the attacker perspective, but the vulnerable feature is configuration-dependent and not a default Internet-exposed service by itself. Namespaces and containers do not significantly improve attacker reachability unless an untrusted tenant can configure host netfilter OSF rules, which would usually require CAP_NET_ADMIN. Ordinary packet senders can only trigger the parsing path after an administrator has already installed the relevant rule. ## 4. Severity interpretation This behaves like an actionable Moderate rather than a clear Important-class vulnerability. The realistic impact is incorrect matching or logging, with possible DoS from an invalid read in a packet-processing path. The theoretical risk is higher because the issue is remotely triggerable in affected configurations and is explicitly an out-of-bounds read, but the patch does not support privilege escalation, arbitrary memory corruption, or a strong confidentiality primitive. The paranoid score is therefore useful for manual-review sensitivity, but it should not be treated as strong LPE or generic kernel memory corruption. ## 5. One-sentence report phrase A remote TCP packet can trigger an out-of-bounds read in nfnetlink_osf option matching when OSF all-match logging is configured, causing incorrect fingerprint results and possible DoS, but no write primitive or privilege escalation path is shown. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the bug is network-triggerable in affected netfilter OSF configurations and is described as an out-of-bounds read in a kernel packet-processing path. Manual review should confirm whether the read can escape skb-owned memory, cause a reliable crash, or disclose observable kernel data through logs or match behavior. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: nfnetlink_osf: fix out-of-bounds read on option matching [ Upstream Commit: 0145548346c4a30981a870a8ca00eac46ba27e85 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0145548346c4a30981a870a8ca00eac46ba27e85 Changed files: net/netfilter/nfnetlink_osf.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=0145548346c4a30981a870a8ca00eac46ba27e85 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52999 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52999 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:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/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: 3 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: NO 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).