From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-52929][MODERATE 7.0] sctp: stream: fully roll back denied add-stream state Date: Wed, 24 Jun 2026 04:11:03 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-52929 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 0cd2dc6dce8ca47212cd306ccd52eb315ef3cf85 List-Id: CVE: CVE-2026-52929 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: sctp: stream: fully roll back denied add-stream state Commit: 0cd2dc6dce8ca47212cd306ccd52eb315ef3cf85 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0cd2dc6dce8ca47212cd306ccd52eb315ef3cf85 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52929 Analysis date: Wed, 24 Jun 2026 04:11:03 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A remote SCTP peer may trigger incomplete rollback of denied ADD_OUT_STREAMS state, causing stale scheduler metadata to be reused and leading to a NULL pointer dereference and kernel DoS. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52929 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52929 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-2026-52929 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-703;*CWE-664;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A NULL pointer dereference in the SCTP stream scheduler path can occur because a denied ADD_OUT_STREAMS rollback only shrank the stream count and did not fully remove scheduler private state for the removed outgoing streams. A remote SCTP peer can potentially trigger the inconsistent state by denying an add streams operation and causing a later re-add to reuse stale stream ext metadata, leading to a kernel crash. For the CVSS the PR:N because the attacker does not need a local account on the victim when they can participate as an SCTP peer and influence the stream reset response. The base score uses AC:H because the sequence depends on SCTP stream reconfiguration and a later re-add path. The paranoid score uses AC:L for deployments where applications commonly use dynamic stream addition and the peer can reliably drive denied responses. The issue is network reachable only where SCTP is enabled and exposed to untrusted peers. Impact is denial of service via kernel crash.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES SIMPLEFIX NETWORK LINUS DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Remote reachable / network-triggerable: +2 The affected path processes SCTP stream reset responses. A peer participating in an SCTP association can influence ADD_OUT_STREAMS denial handling. * Reliable kernel crash / strong DoS: +1 The commit explicitly describes a later re-add reusing stale stream metadata and hitting a NULL pointer dereference in the scheduler get path. * Availability impact realistic: +1 A kernel NULL pointer dereference in this path can crash the host, depending on kernel panic settings and fault handling. * Hard or unreliable sequence required: -1 The trigger depends on a specific SCTP stream reconfiguration sequence: add streams, denial, incomplete rollback, later re-add, and scheduler access. * Net conservative total: 3 Paranoid additional interpretation: * Common networking protocol control path: +1 Although SCTP exposure is less common than TCP or UDP, this is still an in-kernel network protocol parsing/control path reachable by a remote peer when SCTP is exposed. * No hard-race penalty in favorable deployments: +0 instead of -1 In SCTP deployments that actively use dynamic stream reconfiguration, a peer may be able to drive the denied ADD_OUT_STREAMS and re-add sequence more reliably. * Net paranoid total: 5 Not counted: * Generic memory corruption: +0 The patch supports stale scheduler-private state and NULL pointer dereference, but not UAF reclaim, OOB write, arbitrary write, type confusion, or callback hijack. * Privilege escalation plausible: +0 No concrete LPE primitive is shown. * Confidentiality / integrity impact: +0 The evidence supports DoS only. ## 3. Reachability analysis The likely attacker is a remote SCTP peer that can establish or participate in an SCTP association and influence stream reset behavior. No local account on the victim is required in the network-exposed case. This is not a default Internet-wide exposure for most systems because SCTP services are uncommon compared with TCP services and may be filtered by firewalls. However, if an SCTP endpoint is exposed to untrusted peers, the vulnerable code is reachable through protocol control messages. Namespaces and containers do not materially reduce the remote case. For local testing or local SCTP endpoints, unprivileged local code may also be able to create SCTP sockets depending on kernel configuration and policy, but the more important triage path is remote peer influence. ## 4. Severity interpretation This behaves like an actionable remote DoS rather than an Important-class memory corruption issue. The stale stream metadata is security-relevant because it survives rollback and is later reused, but the demonstrated downstream primitive is a NULL pointer dereference, not attacker-controlled memory corruption. The conservative score is borderline because the trigger sequence is specialized. The paranoid score reaches actionable Moderate because the bug is remotely reachable in exposed SCTP deployments and can crash the kernel. ## 5. One-sentence report phrase A remote SCTP peer may trigger incomplete rollback of denied ADD_OUT_STREAMS state, causing stale scheduler metadata to be reused and leading to a NULL pointer dereference and kernel DoS. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the issue is network reachable in SCTP deployments and can cause a kernel crash, even though current evidence supports DoS only and does not show privilege escalation or a strong memory corruption primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: sctp: stream: fully roll back denied add-stream state Commit: 0cd2dc6dce8ca47212cd306ccd52eb315ef3cf85 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0cd2dc6dce8ca47212cd306ccd52eb315ef3cf85 Commit description: When ADD_OUT_STREAMS is denied, SCTP only shrinks the queued chunks and then lowers outcnt. That leaves removed stream metadata behind, so a later re-add can reuse a stale ext and hit a null-pointer dereference in the scheduler get path. Fix the rollback by tearing down the removed stream state the same way other stream resizes do. Unschedule the current scheduler state, drop the removed stream ext state with sctp_stream_outq_migrate(), and then reschedule the remaining streams. This keeps scheduler-private RR/FC/PRIO lists consistent while fully rolling back denied outgoing stream additions. Fixes: 637784a ("sctp: introduce priority based stream scheduler") Cc: stable@kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Zhengchuan Liang Reported-by: Xin Liu Signed-off-by: Wyatt Feng Signed-off-by: Ren Wei Acked-by: Xin Long Link: https://patch.msgid.link/d78954ecd94954653ee299400e98d74a03a6f7d3.1780603399.git.bronzed_45_vested@icloud.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: net/sctp/stream.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=0cd2dc6dce8ca47212cd306ccd52eb315ef3cf85 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52929 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52929 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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 7.5 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: 3 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: NO 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).