From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46015][MODERATE 7.0] tcp: call sk_data_ready() after listener migration Date: Wed, 27 May 2026 16:42:34 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46015 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: 6 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: ab5fdcd535645f6dbe6e9e21d96a08d141e88b4b List-Id: CVE: CVE-2026-46015 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: tcp: call sk_data_ready() after listener migration Commit: ab5fdcd535645f6dbe6e9e21d96a08d141e88b4b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ab5fdcd535645f6dbe6e9e21d96a08d141e88b4b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46015 Analysis date: Wed, 27 May 2026 16:42:34 -0400 ActionableScore: 6 ActionableScore lower bound: 4 Actionable bucket: 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-2026-46015 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46015 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-2026-46015 MODERATE 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-362;*CWE-416;CWE-667;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'TCP listener migration in SO_REUSEPORT can add a child socket to the target accept queue without waking poll or blocking accept waiters, leaving server workers asleep. The same post migration path can dereference nsk after the migrated request has transferred the listener reference and another CPU may drop it, so the code needs RCU protection around sock_net(nsk) and sk_data_ready(). For the CVSS the PR:L is used because reliable triggering requires local control over a SO_REUSEPORT listener group or a cooperating service restart path, while remote clients can only assist by creating queued connections. The issue is not a pure remote packet parser bug. Impact is mainly denial of service, with paranoid memory lifetime concern due to possible stale listener dereference.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) MAYBE REMOTE LOCK NETWORK HARDWARE KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=4 1. ActionableScore * Conservative score: 4 * Paranoid score: 6 * Final recommended bucket: **Actionable Moderate at minimum**:: 2. Signal breakdown * Local unprivileged trigger: +1. Reliable triggering requires control over a `SO_REUSEPORT` listener group or a cooperating local service lifecycle such as listener shutdown or restart. * Real lifetime corruption: +1. After `inet_csk_reqsk_queue_add()` succeeds, the listener reference can be transferred to `nreq->rsk_listener` and dropped by another CPU, making later `nsk` dereferences require RCU protection. * Reliable DoS: +1. Missing `sk_data_ready()` can leave `poll()`, `epoll_wait()`, or blocking `accept()` waiters asleep indefinitely. * Availability impact realistic: +1. The practical effect is service-level DoS from stuck accept waiters or unsafe listener dereference during migration. * Common networking core path: +1. This is TCP listener and `SO_REUSEPORT` accept-queue migration logic. * Hard race / special timing required: -1. The lifetime concern requires concurrent listener migration, accept, shutdown, or reference drop timing. * Paranoid memory corruption / UAF concern: +2. The missing RCU read-side protection indicates a possible stale listener dereference after reference transfer, but no controlled UAF reclaim or LPE primitive is demonstrated. 3. Reachability analysis Remote clients can help populate accept queues, but they cannot reliably trigger the bug alone. Practical triggering requires local or service-level control over a `SO_REUSEPORT` listener group and listener shutdown or migration timing. Containers may matter if an untrusted workload can run a TCP service with `SO_REUSEPORT` on the host kernel. The path is not a pure remote packet parser bug, but it is in common TCP infrastructure. 4. Severity interpretation This is more than a simple missed wakeup because the patch also adds RCU protection for post-migration `nsk` dereferences. The realistic impact is DoS through stuck accept waiters or service disruption. The paranoid concern is stale listener dereference in TCP core, but the patch does not prove arbitrary write, controlled UAF reclaim, information disclosure, or privilege escalation. 5. One-sentence report phrase TCP `SO_REUSEPORT` listener migration can miss wakeups for migrated accept-queue entries and may dereference a target listener after its reference is dropped, causing service DoS and a limited RCU lifetime concern. 6. Manual review recommendation MANUAL CHECK REQUIRED. This touches TCP core listener migration and includes an RCU lifetime issue, although current evidence supports DoS more strongly than practical privilege escalation. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: tcp: call sk_data_ready() after listener migration Commit: ab5fdcd535645f6dbe6e9e21d96a08d141e88b4b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ab5fdcd535645f6dbe6e9e21d96a08d141e88b4b Commit description: When inet_csk_listen_stop() migrates an established child socket from a closing listener to another socket in the same SO_REUSEPORT group, the target listener gets a new accept-queue entry via inet_csk_reqsk_queue_add(), but that path never notifies the target listener's waiters. A nonblocking accept() still works because it checks the queue directly, but poll()/epoll_wait() waiters and blocking accept() callers can also remain asleep indefinitely. Call READ_ONCE(nsk->sk_data_ready)(nsk) after a successful migration in inet_csk_listen_stop(). However, after inet_csk_reqsk_queue_add() succeeds, the ref acquired in reuseport_migrate_sock() is effectively transferred to nreq->rsk_listener. Another CPU can then dequeue nreq via accept() or listener shutdown, hit reqsk_put(), and drop that listener ref. Since listeners are SOCK_RCU_FREE, wrap the post-queue_add() dereferences of nsk in rcu_read_lock()/rcu_read_unlock(), which also covers the existing sock_net(nsk) access in that path. The reqsk_timer_handler() path does not need the same changes for two reasons: half-open requests become readable only after the final ACK, where tcp_child_process() already wakes the listener; and once nreq is visible via inet_ehash_insert(), the success path no longer touches nsk directly. Fixes: 54b92e8 ("tcp: Migrate TCP_ESTABLISHED/TCP_SYN_RECV sockets in accept queues.") Cc: stable@vger.kernel.org Suggested-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Signed-off-by: Zhenzhong Wu Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260422024554.130346-2-jt26wzz@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: net/ipv4/inet_connection_sock.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=ab5fdcd535645f6dbe6e9e21d96a08d141e88b4b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46015 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46015 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: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: 4 Paranoid ActionableScore: 6 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).