From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72136][MODERATE 7.0] xfrm: xfrm_interface: require CAP_NET_ADMIN in the device netns for changelink Date: Sat, 15 Aug 2026 18:26:40 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72136 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 04c1aa57d08471b1953bf27c84ac9b3d78d71831 List-Id: CVE: CVE-2026-72136 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: xfrm: xfrm_interface: require CAP_NET_ADMIN in the device netns for changelink Commit: 04c1aa57d08471b1953bf27c84ac9b3d78d71831 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=04c1aa57d08471b1953bf27c84ac9b3d78d71831 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72136 Analysis date: Sat, 15 Aug 2026 18:26:40 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72136 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72136 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-2026-72136 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:H';CWE-863;CWE-269;CWE-284;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:L';BEST CVSS score: '8.7';DESCR 'xfrm_interface changelink missed a capability check against the interface link network namespace. A caller with CAP_NET_ADMIN in dev_net(dev) but not in xi net could modify an XFRM interface that logically belongs to another network namespace after the device was created in or moved across namespaces. For the CVSS the PR:L is used because the attacker needs limited network administration capability in one namespace, but not full administrative control of the target namespace being modified. The issue is not directly network reachable and is triggered through local rtnetlink control plane operations. Impact is unauthorized cross namespace network configuration modification, with possible disruption or policy impact for XFRM/IPsec interfaces. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES SIMPLEFIX HARDWARE KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS8.5PLUS KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: 2. Signal breakdown * Security-boundary bypass with practical sensitive-object access: +2. The bug bypasses the intended network namespace capability boundary and allows modifying an XFRM interface in `xi->net` without `CAP_NET_ADMIN` there. * Cross-boundary isolation/policy bypass: +1. This is a namespace/capability separation issue, relevant to containers or delegated network administration. * Integrity impact plausible: +1. Unauthorized `changelink` can alter XFRM interface parameters and affect IPsec/XFRM policy behavior. * Availability impact realistic: +1. Misconfiguration of XFRM interfaces can disrupt protected tunnels or network connectivity. * Requires delegated CAP_NET_ADMIN-like privilege: -1 conservative. The attacker is not fully unprivileged, but this is not equivalent to full host root because the bug bypasses a different namespace capability boundary. * No memory corruption signals. No UAF, OOB, arbitrary write, refcount misuse, or lifetime primitive is shown by the patch. 3. Reachability analysis The bug is triggered locally through rtnetlink `changelink` operations on an XFRM interface. The attacker needs `CAP_NET_ADMIN` in `dev_net(dev)`, but the flaw is that they do not need `CAP_NET_ADMIN` in the interface link namespace `xi->net`. This matters in namespace and container scenarios where a process has network administration rights in one namespace but should not control objects owned by another namespace. The path is not directly network reachable. XFRM/IPsec is not universal on all systems, but it is a security-relevant networking subsystem and should not be treated as a rare-only configuration. 4. Severity interpretation This behaves more like an actionable Moderate or Important-candidate access-control bug, not a memory corruption issue. Realistic impact is unauthorized cross-namespace network configuration modification, with possible XFRM/IPsec policy disruption. There is no evidence of direct privilege escalation to host root or arbitrary kernel memory corruption, but the capability and namespace boundary bypass is meaningful enough to avoid auto-closure. 5. One-sentence report phrase An XFRM interface `changelink` authorization bug allowed a caller with `CAP_NET_ADMIN` in one network namespace to modify an interface linked to another namespace without the required capability there, potentially bypassing namespace isolation and disrupting XFRM/IPsec policy. 6. Manual review recommendation MANUAL CHECK REQUIRED. This is a capability and namespace-boundary bypass rather than a simple DoS or validation cleanup, and container or delegated `CAP_NET_ADMIN` deployments can materially change the practical severity. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xfrm: xfrm_interface: require CAP_NET_ADMIN in the device netns for changelink Commit: 04c1aa57d08471b1953bf27c84ac9b3d78d71831 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=04c1aa57d08471b1953bf27c84ac9b3d78d71831 Commit description: xfrmi_changelink() operates on at most two netns, dev_net(dev) and the interface link netns xi->net. They differ once the device is created in or moved to a netns other than the one the request runs in. The rtnl changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a caller privileged there but not in xi->net can rewrite an interface that lives in xi->net. Gate xfrmi_changelink() on rtnl_dev_link_net_capable() at its top, before any attribute is parsed. Reported-by: Xiao Liang Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@mail.gmail.com/ Fixes: f203b76 ("xfrm: Add virtual xfrm interfaces") Cc: stable@vger.kernel.org Signed-off-by: Maoyi Xie Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260612085941.3158249-8-maoyixie.tju@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: net/xfrm/xfrm_interface_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=04c1aa57d08471b1953bf27c84ac9b3d78d71831 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72136 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72136 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:L/PR:L/UI:N/S:C/C:N/I:L/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:H The Best / paranoid CVSS score: 8.7 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: 4 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: 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).