From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80738][MODERATE REGULAR] bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie [ Upstream Date: Thu, 03 Sep 2026 05:40:13 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80738 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 23f682083aa3fbc0c49667818efd6979a8bc5ac2 List-Id: CVE: CVE-2026-80738 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie [ Upstream Commit: 23f682083aa3fbc0c49667818efd6979a8bc5ac2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=23f682083aa3fbc0c49667818efd6979a8bc5ac2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80738 Analysis date: Thu, 03 Sep 2026 05:40:13 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline Moderate, manual review recommended Manual review required: YES Summary: bpf_tcp_gen_syncookie() and bpf_tcp_check_syncookie() could read sk_protocol before confirming a full TCP LISTEN socket, allowing a privileged local BPF program to trigger an invalid kernel read and possible DoS. For the CVSS the PR:L is appropriate when delegated BPF or network administration capability is sufficient, but typical deployments still require privileged BPF access. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80738 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80738 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 REGULAR 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-2026-80738 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80738 CHECK WITH IMPACT FROM ORIG NN MODERATE 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:N/A:H';CWE-843;CWE-125;*CWE-20;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '5.5';DESCR 'bpf_tcp_gen_syncookie() and bpf_tcp_check_syncookie() could read sk sk_protocol before confirming that the supplied sock_common pointer refers to a full TCP LISTEN socket. A local BPF program can pass or receive a mini-socket style object where sk_state is valid but sk_protocol is a fullsock specific field, which can cause an invalid kernel read and potentially a crash. For the CVSS the PR:L is selected because triggering requires local ability to load or run the relevant BPF program, often through CAP_BPF, CAP_NET_ADMIN, or a delegated service context rather than remote packet access alone. The issue is not directly network reachable, although traffic may be used to drive the BPF hook after the program is installed. Impact is primarily denial of service via kernel crash. A limited confidentiality impact is kept only in the paranoid interpretation because the primitive is an invalid read without evidence of an arbitrary write or confirmed privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate, manual review recommended (with actual score 3) YES REMOTE BPF SIMPLEFIX NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline Moderate, manual review recommended**:: ## 2. Signal breakdown * Weak/indirect corruption candidate: +1. The helper accepts ARG_PTR_TO_BTF_ID_SOCK_COMMON but reads sk_protocol before proving that the object is a full socket. This is an invalid struct interpretation / wrong object field access. * Reliable kernel crash / strong DoS: +1. The patch prevents dereferencing a fullsock-specific field on mini-socket objects, which can plausibly lead to an invalid kernel read and crash. * Weak LPE concern, paranoid only: +1. This is not a proven LPE primitive, but BPF helper type handling and socket object confusion justify manual review in the paranoid score. * Requires privileged BPF access in typical deployments: -2 conservative. Loading or attaching the relevant BPF program normally requires CAP_BPF, CAP_NET_ADMIN, CAP_SYS_ADMIN, root, or a privileged service context. * Reduced-capability or delegated context adjustment: -1 paranoid. In some environments, container root, delegated CAP_BPF, delegated CAP_NET_ADMIN, or service-managed BPF may be less than full host root. ## 3. Reachability analysis The bug is locally reachable through BPF helper use, not directly through unauthenticated network traffic. Network packets may help exercise the installed BPF program, but the attacker first needs the ability to load or run the relevant BPF program. In typical hardened product configurations where unprivileged BPF is disabled, this is privileged local attack surface. Namespace and container setups matter because delegated CAP_BPF or CAP_NET_ADMIN can make the practical privilege level closer to PR:L than full host-root, but this still is not PR:N. Call-site confidence: high, because the affected helper checks and field access order are visible in the supplied patch. ## 4. Severity interpretation This behaves more like a Moderate BPF type handling bug with possible local DoS than an Important-class vulnerability. The concrete primitive is an invalid read / wrong object interpretation, not UAF, OOB write, refcount takeover, callback control, or arbitrary write. Theoretical privilege escalation concern is weak and based only on BPF object type confusion risk, so it should not be scored as strong memory corruption without further evidence. ## 5. One-sentence report phrase bpf_tcp_gen_syncookie() and bpf_tcp_check_syncookie() could read sk_protocol before confirming a full TCP LISTEN socket, allowing a privileged local BPF program to trigger an invalid kernel read and possible DoS. For the CVSS the PR:L is appropriate when delegated BPF or network administration capability is sufficient, but typical deployments still require privileged BPF access. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED. YES REQUIRES MANUAL CHECK. Reason: BPF helper type handling and mini-socket versus full-socket interpretation deserve review, but current evidence supports invalid read / DoS rather than confirmed LPE. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie [ Upstream Commit: 23f682083aa3fbc0c49667818efd6979a8bc5ac2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=23f682083aa3fbc0c49667818efd6979a8bc5ac2 Changed files: net/core/filter.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=23f682083aa3fbc0c49667818efd6979a8bc5ac2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80738 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80738 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:N/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: 2 Paranoid ActionableScore: 3 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 REGULAR 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).