From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80637][MODERATE REGULAR] netfilter: synproxy: fix unaligned memory access in timestamp adjustment [ Upstream Date: Fri, 28 Aug 2026 04:48:46 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80637 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: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 2b8e7aaa38002d8ee2f48d87b1f392eadd8e98c4 List-Id: CVE: CVE-2026-80637 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: netfilter: synproxy: fix unaligned memory access in timestamp adjustment [ Upstream Commit: 2b8e7aaa38002d8ee2f48d87b1f392eadd8e98c4 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b8e7aaa38002d8ee2f48d87b1f392eadd8e98c4 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80637 Analysis date: Fri, 28 Aug 2026 04:48:46 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: A remote peer may trigger an unaligned memory access in netfilter SYNPROXY timestamp adjustment on strict alignment architectures, causing a kernel crash when traffic reaches an active SYNPROXY rule. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80637 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80637 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-2026-80637 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-704;CWE-758;CWE-703;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'SYNPROXY timestamp adjustment can access TCP timestamp fields through direct 32 bit pointer dereferences even though TCP options are byte aligned and may not be naturally aligned. A remote peer can potentially trigger the fault by sending TCP packets with timestamp options through an active SYNPROXY rule, causing an unaligned access exception and kernel crash on strict alignment architectures. For the CVSS the PR:N is used because no attacker privileges are required beyond network reachability to the protected SYNPROXY path. The issue is network reachable when SYNPROXY is configured on a reachable firewall or gateway. Impact is denial of service only because the patch indicates an unaligned access fault rather than UAF, OOB write, information disclosure, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4) YES REMOTE DANGER SIMPLEFIX NETFILTER HARDWARE INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Borderline, manual review recommended**:: ## 2. Signal breakdown Triggered signals: * Remote reachable / network-triggerable: +2 SYNPROXY is in the netfilter packet path, and a remote peer can influence TCP timestamp option layout when traffic reaches an active SYNPROXY rule. * Reliable kernel crash / strong DoS: +1 The commit explicitly says unaligned memory access can cause a crash on strict alignment architectures. * Common networking core path or packet-processing path: +1 This is packet-processing code in netfilter SYNPROXY. Subtract signals: * Rare AND difficult-to-reach subsystem/configuration: -1 conservative only Practical crash impact depends on SYNPROXY being configured and on a strict alignment architecture. On common tolerant architectures such as x86, the issue is more likely performance degradation than crash. Not awarded: * Generic memory corruption: +0 The patch shows unsafe unaligned 32 bit loads/stores, not UAF, OOB write, type confusion, double free, or arbitrary write. * Privilege escalation plausible: +0 No supported LPE primitive is visible. * Confidentiality / Integrity impact: +0 No information leak or unauthorized modification primitive is shown. ## 3. Reachability analysis An unauthenticated remote host may trigger the affected code path if its TCP traffic is processed by a reachable netfilter SYNPROXY configuration with timestamp adjustment active. No local account is needed for the attacker in that deployment, so PR:N is reasonable for CVSS-style reachability. The path is not enabled by default on all systems because SYNPROXY requires explicit firewall configuration. The crash condition is also architecture-dependent because strict alignment architectures are affected more severely than x86-like architectures. ## 4. Severity interpretation This behaves like an actionable network-reachable DoS issue, not an Important-class memory corruption vulnerability. The realistic impact is kernel crash or performance degradation on specific deployments. Theoretical escalation is not supported because the patch only replaces direct unaligned timestamp access with get_unaligned_be32() and put_unaligned_be32(), and there is no evidence of attacker-controlled overwrite beyond the intended TCP option field. ## 5. One-sentence report phrase A remote peer may trigger an unaligned memory access in netfilter SYNPROXY timestamp adjustment on strict alignment architectures, causing a kernel crash when traffic reaches an active SYNPROXY rule. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the issue is network-triggerable in packet-processing code, but real severity depends strongly on SYNPROXY deployment and CPU alignment behavior. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: synproxy: fix unaligned memory access in timestamp adjustment [ Upstream Commit: 2b8e7aaa38002d8ee2f48d87b1f392eadd8e98c4 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b8e7aaa38002d8ee2f48d87b1f392eadd8e98c4 Changed files: net/netfilter/nf_synproxy_core.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=2b8e7aaa38002d8ee2f48d87b1f392eadd8e98c4 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80637 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80637 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:N/A:H The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 7.5 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: 3 Paranoid ActionableScore: 4 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).