From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-63870][MODERATE REGULAR] ieee802154: 6lowpan: only accept IPv6 packets in lowpan_xmit() [ Upstream Date: Sun, 19 Jul 2026 11:02:33 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-63870 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: 2 X-AL-KERNEL-Commit: af07fffbd53ddc3ec3c2a4ca914f27899fa89bca List-Id: CVE: CVE-2026-63870 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ieee802154: 6lowpan: only accept IPv6 packets in lowpan_xmit() [ Upstream Commit: af07fffbd53ddc3ec3c2a4ca914f27899fa89bca Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=af07fffbd53ddc3ec3c2a4ca914f27899fa89bca Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63870 Analysis date: Sun, 19 Jul 2026 11:02:33 -0400 ActionableScore: 4 ActionableScore lower bound: 2 Actionable bucket: Borderline Moderate / manual review recommended Manual review required: YES Summary: A non IPv6 skb queued to an ieee802154 6LoWPAN interface can cause `lowpan_xmit()` to use uninitialized `lowpan_addr_info`, potentially leading to malformed transmission behavior or limited kernel data disclosure, but exploitation appears local or configuration dependent rather than directly remote. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63870 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63870 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-2026-63870 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-457;CWE-908;*CWE-200;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.8';DESCR 'The 6LoWPAN transmit path can use uninitialized lowpan_addr_info when a non IPv6 skb is queued to a 6LoWPAN interface. The header creation path may return without initializing this metadata, while lowpan_xmit() later treats it as valid input for header construction. This is primarily a local or locally configured network stack issue rather than a directly remote packet processing flaw. For the CVSS the PR:L is used because triggering requires a local process or delegated capability able to inject or route a non IPv6 packet through the 6LoWPAN transmit path. Impact is at least a local denial of service or malformed transmit behavior, with possible limited confidentiality impact if uninitialized kernel data is copied into an outgoing frame. The paranoid score keeps the same bug class and raises impact only to the highest still defensible interpretation for manual review sensitivity.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate / manual review recommended (with actual score 3) YES INIT SIMPLEFIX SKB LINUS TEST IPV6 SYZBOT PACKET INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 4 * Final recommended bucket: **Borderline Moderate / manual review recommended**:: ## 2. Signal breakdown Conservative signals: * Local trigger: +1. A local process or locally configured test path can queue a non IPv6 skb through a 6LoWPAN interface. * Weak indirect corruption candidate: +1. The bug uses uninitialized `lowpan_addr_info` as transmit metadata, but the patch does not show UAF, OOB write, arbitrary write, or controlled object replacement. * Confidentiality impact plausible: +1. Uninitialized kernel metadata may influence or be copied into an outgoing frame. * Rare and difficult to reach subsystem/configuration: -1. 6LoWPAN over ieee802154 is not a broad default path and triggering needs unusual interface setup. Paranoid additional signals: * Integrity impact plausible: +1. Uninitialized address metadata may affect header construction or packet destination semantics. * Availability impact plausible: +1. Malformed transmit behavior or driver/network stack errors are possible, but no reliable crash primitive is shown. * Same rare configuration penalty remains: -1. No strong memory corruption, no Dirty Pipe like primitive, no demonstrated LPE path, and no direct remote reachability are supported by the patch. ## 3. Reachability analysis The realistic trigger is local or locally configured: a non IPv6 packet must be queued for transmission on a 6LoWPAN interface. This likely requires either local packet injection plus an existing misconfigured 6LoWPAN device, or administrative/delegated network setup such as CAP_NET_ADMIN in a namespace. It is not a normal remote receive path and should not be scored as directly network reachable. Namespace setups may reduce practical privileges if untrusted users can create or control the relevant netdev topology, but typical production exposure is limited. Call-site confidence: medium. The commit explains the relevant call path from header creation to `lowpan_xmit()`, but the full caller graph is not present in the provided diff. ## 4. Severity interpretation This behaves more like a borderline Moderate issue than an Important-class vulnerability. The strongest supported primitive is use of uninitialized kernel data in a network transmit metadata path. Theoretical confidentiality or malformed packet effects are plausible, but there is no evidence of attacker-controlled memory corruption, privilege escalation, arbitrary write, UAF reclaim, or a reliable host crash. Manual review is still useful because uninitialized kernel data can sometimes become an information disclosure depending on the exact transmitted header contents. ## 5. One-sentence report phrase A non IPv6 skb queued to an ieee802154 6LoWPAN interface can cause `lowpan_xmit()` to use uninitialized `lowpan_addr_info`, potentially leading to malformed transmission behavior or limited kernel data disclosure, but exploitation appears local or configuration dependent rather than directly remote. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the issue is not strong enough for Important by itself, but uninitialized kernel data is used in a network transmit path, so the possible information disclosure surface should be manually checked before auto-closing. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ieee802154: 6lowpan: only accept IPv6 packets in lowpan_xmit() [ Upstream Commit: af07fffbd53ddc3ec3c2a4ca914f27899fa89bca Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=af07fffbd53ddc3ec3c2a4ca914f27899fa89bca Changed files: net/bluetooth/6lowpan.c net/ieee802154/6lowpan/tx.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=af07fffbd53ddc3ec3c2a4ca914f27899fa89bca ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63870 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63870 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:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 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).