From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-63971][MODERATE 7.0] sctp: fix race between sctp_wait_for_connect and peeloff [ Upstream Date: Sun, 19 Jul 2026 20:21:31 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-63971 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: 0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d List-Id: CVE: CVE-2026-63971 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: sctp: fix race between sctp_wait_for_connect and peeloff [ Upstream Commit: 0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63971 Analysis date: Sun, 19 Jul 2026 20:21:31 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A local SCTP user can race connect waiting with SCTP peeloff so that an association migrates to another socket while the sender continues under the wrong lock, causing at least local DoS and requiring manual review for possible race-dependent memory corruption. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63971 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63971 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-2026-63971 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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-667;*CWE-416;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in SCTP connect waiting can occur because sctp_wait_for_connect drops the socket lock while waiting and then re-acquires the old socket lock without verifying that the association still belongs to that socket. A local process using SCTP can race this path with SCTP_SOCKOPT_PEELOFF so that asoc base sk is migrated to a new socket while the sender continues under the wrong lock in sctp_datamsg_from_user. For the CVSS the PR:L is used for the paranoid score because an unprivileged local user or process with access to SCTP sockets can potentially create the racing threads and invoke peeloff without full administrative privileges. The issue is not directly network reachable because the critical peeloff operation is a local socket control operation. Impact is at least local denial of service via kernel crash or lock corruption. In the worst still defensible interpretation, wrong-lock access to an SCTP association may allow memory corruption or use-after-free effects, so confidentiality and integrity are included in the paranoid score for manual-review sensitivity.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES SIMPLEFIX RACE NETWORK LINUS KPANIC KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1 A local process with access to SCTP sockets can create the relevant association and race `sctp_wait_for_connect()` with `SCTP_SOCKOPT_PEELOFF`. * Memory corruption, weak/indirect corruption candidate: +1 The caller may continue using an SCTP association under the wrong socket lock after `asoc->base.sk` has migrated. The patch does not show a direct write primitive, but wrong-lock access to a shared protocol object is a credible corruption candidate. * Reliable kernel crash / strong DoS: +1 The likely practical impact is inconsistent locking and object access in the SCTP send path, which can plausibly lead to crash, lock corruption, or kernel warning/failure. * Networking socket/protocol exposure: +1 SCTP is a kernel networking protocol exposed through normal socket APIs. This is not remotely triggerable by packets alone, but it is more security-relevant than a private driver cleanup path. Paranoid additional signal: * Weak LPE concern: +1 In the worst still-defensible interpretation, accessing an association under the wrong lock could enable stale object use or race-dependent memory corruption. There is no demonstrated reclaim or controlled overwrite, so this is only a weak LPE concern, not a strong LPE primitive. Negative signals: * Hard or timing-dependent race: not subtracted in the main score Although this is a race, the window is intentionally created by `sctp_wait_for_connect()` dropping the socket lock while sleeping. A local attacker can likely improve reliability with two coordinated threads and SCTP state control. ## 3. Reachability analysis The bug is locally triggerable through SCTP socket operations. The critical operation is `getsockopt(SCTP_SOCKOPT_PEELOFF)`, so this is not directly network reachable by a remote peer without local code execution. A remote SCTP peer may help create protocol state, but the actual race requires a local process controlling the socket. Privileges are best treated as PR:L for practical triage. Full administrative privileges are not inherently required if SCTP socket creation and peeloff are available to the local user. Containers or network namespaces may affect reachability depending on whether SCTP is enabled and exposed inside the namespace. SCTP is not as universally deployed as TCP or UDP, but it is a normal kernel networking protocol and should not be treated as an obscure hardware-only path. ## 4. Severity interpretation This is stronger than an ordinary Moderate because it is a local race in a kernel networking protocol object with wrong-lock access after association migration. The conservative interpretation is local DoS or lock/object-state corruption. The paranoid interpretation does not assume arbitrary code execution. However, wrong-lock access to an SCTP association can plausibly become a memory-lifetime or corruption issue, so it should not be auto-closed without manual review. This is best handled as Actionable Moderate at minimum, with weak Important-candidate concern if follow-up analysis shows stale object reuse, write-after-free, refcount misuse, or attacker-controlled reclaim. ## 5. One-sentence report phrase A local SCTP user can race connect waiting with SCTP peeloff so that an association migrates to another socket while the sender continues under the wrong lock, causing at least local DoS and requiring manual review for possible race-dependent memory corruption. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a race in SCTP association/socket ownership and locking. The patch is small, but the affected caller path uses the association after lock reacquisition, making this a credible wrong-lock and lifetime-corruption candidate even though no concrete LPE primitive is demonstrated. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: sctp: fix race between sctp_wait_for_connect and peeloff [ Upstream Commit: 0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d Changed files: net/sctp/socket.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=0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63971 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63971 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: 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).