From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46116][IMPORTANT] xfrm: defensively unhash xfrm_state lists in __xfrm_state_delete [ Upstream Date: Thu, 28 May 2026 14:28:58 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46116 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 7 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: b4a53add2fa8f1b5aa17d4c5686c320785fab182 List-Id: CVE: CVE-2026-46116 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: xfrm: defensively unhash xfrm_state lists in __xfrm_state_delete [ Upstream Commit: b4a53add2fa8f1b5aa17d4c5686c320785fab182 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b4a53add2fa8f1b5aa17d4c5686c320785fab182 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46116 Analysis date: Thu, 28 May 2026 14:28:58 -0400 ActionableScore: 7 ActionableScore lower bound: 5 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: XFRM state teardown can inconsistently unhash already removed `xfrm_state` list nodes, causing KASAN-confirmed UAF and OOB write behavior with reliable kernel crashes under reachable XFRM lifecycle operations. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46116 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46116 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: IMPORTANT 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-2026-46116 IMPORTANT CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;*CWE-787;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'XFRM state lifecycle handling could delete bydst, bysrc, byseq, or byspi hlist nodes based on stale state and scalar predicates instead of actual list membership. Under teardown or cleanup races this can make __xfrm_state_delete operate on an already removed xfrm_state and write through poisoned list pointers, producing use-after-free and out-of-bounds write behavior observed by KASAN. For the CVSS the PR:L is used in the paranoid delegated namespace model because a container root or service with CAP_NET_ADMIN in a network namespace may be able to exercise XFRM state operations without full host root. AC:H is kept because reliable triggering depends on lifecycle timing, cleanup, and XFRM state transitions. Impact is at least denial of service via kernel crash and in the paranoid case may include confidentiality and integrity impact due to UAF and list metadata corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) MAYBE WRITE OOB DANGER INIT UAF KERNEL_PANIC_PLUS_UAF HARDWARE LINUS KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=5 ## 1. ActionableScore * Conservative score: **5** * Paranoid score: **7** * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown * Local privileged or delegated trigger: **+1**. XFRM state operations usually require `CAP_NET_ADMIN`, but this may be available to container root or delegated network-management services. * Strong memory corruption primitive: **+2**. KASAN reports UAF and an OOB write variant in `xfrm_state` lifecycle handling. * Real lifetime corruption: **+1**. The bug is stale or repeated hlist deletion of `xfrm_state` nodes, including possible second delete of already removed entries. * Weak to strong LPE concern: **+1 paranoid**. UAF plus list metadata writes are concerning, but no controlled reclaim or exploit primitive is demonstrated. * Reliable kernel crash / strong DoS: **+1**. Syzkaller repeatedly reproduced crashes across multiple signatures. * Availability impact realistic: **+1**. Kernel crash is a demonstrated outcome. * Common networking core or important packet/security subsystem: **+1**. XFRM/IPsec is not always enabled, but it is a core kernel networking security subsystem and should not receive a rarity penalty. * Hard lifecycle/race conditions: **-1**. Triggering depends on state lifecycle, netns cleanup, and timing-sensitive transitions. * Typical CAP_NET_ADMIN requirement: **-1 conservative**. Not full host-root necessarily, but ordinary unprivileged users usually cannot manage XFRM state. ## 3. Reachability analysis The issue is local control-plane reachable through XFRM/IPsec state lifecycle operations and netns cleanup paths. In typical deployments, direct triggering requires `CAP_NET_ADMIN` or equivalent network namespace control. Containers matter because `CAP_NET_ADMIN` in a namespace or delegated network-management privileges may lower practical privilege requirements compared with full host root. The issue is not directly remote packet-triggered from the patch evidence. Syzkaller demonstrates realistic crashability once the relevant state transitions are reachable. ## 4. Severity interpretation This behaves like a **Strong Important candidate** under delegated namespace or containerized threat models, and at minimum an actionable Moderate for host-admin-only environments. The realistic demonstrated impact is kernel crash from UAF/OOB write in `xfrm_state` lifecycle. Theoretical escalation is plausible due to lifetime corruption and list metadata writes, but exploitability beyond DoS is not proven. It should not be auto-closed. ## 5. One-sentence report phrase XFRM state teardown can inconsistently unhash already removed `xfrm_state` list nodes, causing KASAN-confirmed UAF and OOB write behavior with reliable kernel crashes under reachable XFRM lifecycle operations. ## 6. Manual review recommendation **MANUAL CHECK REQUIRED** Manual review is required because the patch fixes KASAN-confirmed UAF/OOB write behavior in a core XFRM/IPsec state lifecycle path, with container or namespace delegation potentially reducing required privileges. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xfrm: defensively unhash xfrm_state lists in __xfrm_state_delete [ Upstream Commit: b4a53add2fa8f1b5aa17d4c5686c320785fab182 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b4a53add2fa8f1b5aa17d4c5686c320785fab182 Changed files: include/linux/list.h include/linux/rculist.h net/xfrm/xfrm_state.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=b4a53add2fa8f1b5aa17d4c5686c320785fab182 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46116 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46116 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:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/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: 5 Paranoid ActionableScore: 7 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).