From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98257][MODERATE 7.0] rds: ib: use rds_conn_drop() on protocol version mismatch Date: Sat, 10 Oct 2026 14:21:37 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98257 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: 4 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 424019be3f637da76b74f44a40034669acbb166f List-Id: CVE: CVE-2026-98257 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: rds: ib: use rds_conn_drop() on protocol version mismatch Commit: 424019be3f637da76b74f44a40034669acbb166f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=424019be3f637da76b74f44a40034669acbb166f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98257 Analysis date: Sat, 10 Oct 2026 14:21:37 -0400 ActionableScore: 4 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98257 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98257 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-2026-98257 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98257 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE AEGIS_AS=3 LEGACY=MODERATE_KPANIC RESULT=DIFF (independent Legacy and Aegis differ; FINAL: MODERATE_KPANIC, Aegis: MODERATE) 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-833;CWE-667;CWE-821;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'An RDS/IB connection can deadlock when a remote peer negotiates a protocol version older than RDS_PROTOCOL_COMPAT_VERSION. The RDMA CM event handler calls synchronous connection destruction while holding c_cm_lock, and the resulting flush waits for shutdown work that needs the same lock. This circular wait can permanently stall the RDS connection workqueues and cause denial of service for RDS communication. For the CVSS the PR:N is selected because an attacker does not need a local account or privileges on the target and only needs the ability to connect as an RDS/IB peer. The base assessment uses AV:A because RDS/IB is normally reachable only through an RDMA or RoCE fabric. The paranoid assessment uses AV:N for deployments where a routed RoCEv2 endpoint is reachable beyond the adjacent storage network. The demonstrated primitive is a deterministic deadlock rather than memory corruption, so the supported impact is availability loss without confidentiality or integrity impact.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE INIT WARNONLY SIMPLEFIX LINUS KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 4 * Conservative score: 4 * Raw paranoid score: 4 * Paranoid score: 4 * No floor or cap was applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +2 Remote network trigger: an RDS/IB peer can select an obsolete protocol version and directly reach the vulnerable RDMA-CM completion path. * +1 Strong DoS: the synchronous `rds_conn_destroy()` call creates a deterministic circular wait between the event handler holding `c_cm_lock` and shutdown work requiring `cp_cm_lock`. * +1 Persistent subsystem impact: the deadlock blocks shared RDS connection workqueues indefinitely, extending the effect beyond failure of the initiating connection. * No privilege penalty: the remote peer does not require administrative privileges on the victim. * No race penalty: the failure follows a deterministic lock and `flush_work()` sequence rather than a narrow timing window. * No rarity penalty: RDS/IB requires an exposed RDMA or RoCE environment, but niche deployment alone does not justify subtraction. * No corruption points: no UAF, OOB access, stale object, refcount mutation, or active-state replacement is established. * No C or I points: the evidence supports availability loss only. * No B5-R signal: there is no retry-accumulated heap OOB write or later consumption of corrupted structured state. * No B3-PENDING signal: no shared-backing or file-backed write exists. * No B4-PENDING signal: no authorization decision or mandatory security check is bypassed. * No additional availability point was added merely for repeatability. The scored persistence point reflects the broader shared-workqueue outage rather than reproduction of the same connection failure. 3. Reachability analysis The attacker is a remote RDS/IB peer with connectivity to the victim RDMA or RoCE endpoint. The peer controls the negotiated protocol version and can select a version below `RDS_PROTOCOL_COMPAT_VERSION`, so no local account, host UID 0, or victim-side administrative capability is required. An operational RDS/IB endpoint and reachable RDMA fabric are prerequisites. This is existing service exposure rather than a privileged action the remote attacker must perform on the victim. Routed RoCEv2 may broaden reachability, while traditional InfiniBand deployments generally constrain it to the adjacent fabric. That deployment distinction does not change the ActionableScore because both paths are network-triggered. No user-namespace or network-namespace capability chain is established, so `NamespaceScopedPrivilege=UNKNOWN`. No special race, retry loop, or attacker-controlled allocator behavior is required. 4. Primitive and severity interpretation The exact primitive is a lock-ordering deadlock. `rds_ib_cm_connect_complete()` calls synchronous destruction while holding the connection CM lock. Destruction flushes shutdown work, but that work requires the same lock and cannot complete. This is not an active-object UAF, fixed stale-storage access, repeated release, or memory-corruption primitive. It is therefore `CLASS_C`. The demonstrated consequence is persistent loss of RDS connection processing. Kernel memory disclosure, state corruption, privilege escalation, and host code execution are unsupported. `ImportantCandidate=NO` because no corruption, ownership violation, authorization bypass, or exploitation leverage beyond denial of service is established. `AutoDowngradeAllowed=YES` because the unresolved facts concern deployment scope, not a hidden corruption primitive. Operational severity is Moderate-like but actionable enough for review where RDS/IB is exposed to untrusted peers. 5. One-sentence report phrase A remote RDS/IB peer can negotiate an obsolete protocol version and trigger a deterministic lock deadlock that permanently stalls RDS connection workqueues, causing subsystem denial of service without demonstrated memory corruption or privilege escalation. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Confirm whether the affected deployment exposes RDS/IB through an untrusted InfiniBand or routed RoCE network and whether the stalled workqueues are shared across all RDS connections. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: rds: ib: use rds_conn_drop() on protocol version mismatch Commit: 424019be3f637da76b74f44a40034669acbb166f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=424019be3f637da76b74f44a40034669acbb166f Commit description: rds_ib_cm_connect_complete() runs from the RDMA-CM event handler with conn->c_cm_lock held. When the peer negotiates a protocol version older than RDS_PROTOCOL_COMPAT_VERSION, the handler calls rds_conn_destroy(), which is only safe in the rmmod path: it synchronously tears the connection down and flush_work()es the shutdown work cp_down_w. That shutdown work (rds_conn_shutdown()) needs cp_cm_lock, which is the very lock the event handler still holds, so the flush never completes: the two workers wait on each other and the RDS connection workqueues stall for good. All other RDMA-CM failure paths (REJECTED, CONNECT_ERROR, DISCONNECTED) use rds_conn_drop(), which marks the connection RDS_CONN_ERROR and schedules the shutdown work asynchronously. Use it here as well. Fixes: f147dd9 ("RDS/IB: Disallow connections less than RDS 3.1") Reported-by: TencentOS Corvus AI Cc: stable@vger.kernel.org Reviewed-by: Allison Henderson Signed-off-by: Aohan Mei Link: https://patch.msgid.link/20260911073436.3542080-1-ljp1205831794@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: net/rds/ib_cm.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=424019be3f637da76b74f44a40034669acbb166f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98257 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98257 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:A/AC:L/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: unknown Paranoid ActionableScore: 4 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).