From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46137][MODERATE REGULAR] mptcp: pm: ADD_ADDR rtx: fix potential data-race [ Upstream Date: Thu, 28 May 2026 13:08:53 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46137 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: 1 X-AL-KERNEL-Commit: 013dcdc1961543b9a3433466bc8c79a2f4ca75b5 List-Id: CVE: CVE-2026-46137 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: mptcp: pm: ADD_ADDR rtx: fix potential data-race [ Upstream Commit: 013dcdc1961543b9a3433466bc8c79a2f4ca75b5 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=013dcdc1961543b9a3433466bc8c79a2f4ca75b5 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46137 Analysis date: Thu, 28 May 2026 13:08:53 -0400 ActionableScore: 3 ActionableScore lower bound: 1 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: A missing socket BH lock in the MPTCP ADD_ADDR retransmission timer can race with socket owner context and may cause inconsistent path-manager state or connection-level DoS, but no memory corruption or privilege escalation primitive is shown. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46137 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46137 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-2026-46137 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-667;CWE-820;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'mptcp_pm_add_timer runs from a softirq timer callback and accessed MPTCP path manager state without taking the socket BH lock, creating a potential data race with socket owner context. The realistic impact is inconsistent ADD_ADDR retransmission state or MPTCP connection level denial of service rather than memory corruption. For the CVSS the PR:N is used in the paranoid network model because a remote MPTCP peer may influence connection state and retransmission timing on an exposed MPTCP service, but AC:H is kept because reliable triggering depends on a race window and specific socket state. No confidentiality or integrity impact is assigned because the patch shows no UAF, OOB write, information leak, or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 2) MAYBE REMOTE DANGER SIMPLEFIX RACE NETWORK TIMER DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: **1** * Paranoid score: **3** * Final recommended bucket: **Borderline, manual review recommended**:: ## 2. Signal breakdown * Local unprivileged trigger: **+1 conservative**. A local unprivileged process can create/use MPTCP sockets if MPTCP is enabled and available. * Remote/network influence: **+2 paranoid**. A remote MPTCP peer may influence connection state and ADD_ADDR retransmission timing, but the patch does not prove a direct remote crash primitive. * Availability impact realistic: **+1 paranoid**. The race may cause inconsistent MPTCP path-manager state or connection-level DoS. * Hard or unreliable race: **-1**. Reliable triggering depends on timing between a softirq timer callback and socket owner context. * No memory corruption: **+0**. The patch shows missing socket locking and data-race prevention, but no UAF, OOB write, heap overwrite, or type confusion. * No confidentiality or integrity signal: **+0**. There is no info leak, arbitrary write, privilege escalation, or security-boundary bypass shown. * Broad/common networking exposure: **0**. MPTCP is a network subsystem, but it is not as broadly exposed as core TCP packet processing and often depends on runtime configuration. ## 3. Reachability analysis The affected code runs from an MPTCP ADD_ADDR retransmission timer in softirq context. A local process using MPTCP can naturally create the socket state involved. A remote MPTCP peer may influence path-manager state and retransmission behavior, but the exploitability remains timing-dependent and the patch does not demonstrate remote packet-triggered kernel memory corruption. Namespaces do not materially change the core issue, except that containers allowed to use MPTCP sockets may provide local trigger surface. MPTCP availability depends on kernel config and runtime deployment. ## 4. Severity interpretation This behaves like a **borderline Moderate** issue. The theoretical concern is a socket-state data race in a network protocol path. The realistic evidence supports MPTCP connection disruption or inconsistent ADD_ADDR retransmission behavior, not privilege escalation or kernel memory corruption. It should not be classified as Important without additional evidence showing a UAF, crash, or reliable remote DoS. ## 5. One-sentence report phrase A missing socket BH lock in the MPTCP ADD_ADDR retransmission timer can race with socket owner context and may cause inconsistent path-manager state or connection-level DoS, but no memory corruption or privilege escalation primitive is shown. ## 6. Manual review recommendation **MANUAL CHECK RECOMMENDED** This is a network-protocol data race with possible remote influence, so it should not be auto-closed immediately, but current evidence supports DoS/state inconsistency only. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mptcp: pm: ADD_ADDR rtx: fix potential data-race [ Upstream Commit: 013dcdc1961543b9a3433466bc8c79a2f4ca75b5 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=013dcdc1961543b9a3433466bc8c79a2f4ca75b5 Changed files: net/mptcp/pm_netlink.c net/mptcp/pm.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=013dcdc1961543b9a3433466bc8c79a2f4ca75b5 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46137 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46137 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:N/I:N/A:L The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.9 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: 1 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).