From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46135][IMPORTANT] nvmet-tcp: fix race between ICReq handling and queue teardown Date: Thu, 28 May 2026 13:16:48 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46135 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 8 X-AL-KERNEL-ActionableScore-Lower: 7 X-AL-KERNEL-Commit: 49891c8fe0cb43fbbe480da1cdccfbbaeb820cb3 List-Id: CVE: CVE-2026-46135 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: nvmet-tcp: fix race between ICReq handling and queue teardown Commit: 49891c8fe0cb43fbbe480da1cdccfbbaeb820cb3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=49891c8fe0cb43fbbe480da1cdccfbbaeb820cb3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46135 Analysis date: Thu, 28 May 2026 13:16:48 -0400 ActionableScore: 8 ActionableScore lower bound: 7 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A race in the NVMe/TCP target ICReq path can let a remote host close the connection during queue teardown and cause a second `kref_put()` on an already released queue, leading to DoS and possible lifetime corruption. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46135 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46135 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: IMPORTANT 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-2026-46135 IMPORTANT CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;CWE-415;CWE-667;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A race in the NVMe TCP target can occur when a host sends ICReq and immediately closes the connection while target side queue teardown is already moving the queue to DISCONNECTING. Later io_work can process the buffered ICReq and overwrite the queue state back to LIVE or FAILED, which can bypass the teardown guard and allow a second kref_put() on an already released queue. For the CVSS the PR:N is used because a remote NVMe TCP host can trigger the ICReq close race when the target listener is reachable, without a local account on the target. AC:H is kept because reliable triggering depends on a teardown timing window. Impact is at least denial of service via kernel crash and in the paranoid case may include confidentiality and integrity impact due to queue lifetime corruption. NVMe TCP targets are usually deployed on isolated storage or data center networks, so AV:A is used instead of broad Internet AV:N.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) MAYBE REMOTE LOCK DANGER INIT NVME RACE NETWORK LINUS KPANIC KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=7 ## 1. ActionableScore * Conservative score: **7** * Paranoid score: **8** * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown * Remote reachable / network-triggerable: **+2**. A remote NVMe/TCP host can send `ICReq` and close the connection when the target listener is reachable. * Strong memory corruption primitive: **+2**. The commit explicitly describes a second `kref_put()` on an already released queue, which is a lifetime corruption / double-release candidate. * Real lifetime corruption: **+1**. This is a queue lifetime bug involving teardown, state rollback, and reference dropping after release. * Weak to moderate LPE concern: **+1**. A double `kref_put()` / released queue path can become UAF-like, but the patch does not show a controlled reclaim or overwrite primitive. * Reliable kernel crash / strong DoS: **+1**. The realistic immediate impact is target kernel crash or service disruption. * Availability impact realistic: **+1**. NVMe/TCP target failure can affect storage availability. * Important filesystem/storage path: **+1**. NVMe/TCP target is a storage transport path. * Hard race / timing required: **-1**. Reliable triggering depends on timing between ICReq processing, connection close, softirq teardown, and later `io_work`. * Configuration-dependent exposure: **-1 conservative only**. NVMe/TCP target must be enabled and reachable. This is not a default Internet-facing service in most deployments. ## 3. Reachability analysis The bug is reachable by a remote NVMe/TCP host that can connect to the target and race ICReq handling with immediate connection teardown. No local account on the target is required if the NVMe/TCP listener is reachable. The practical exposure is usually adjacent or internal storage networks rather than the public Internet. Containers and namespaces are less relevant on the target side, but any workload or host with network access to the NVMe/TCP target could potentially trigger the race. Exploitation reliability is timing-dependent, but the described sequence is realistic for a network client. ## 4. Severity interpretation This behaves like a **Strong Important candidate**. The conservative interpretation is remote-adjacent DoS through a queue teardown race. The paranoid interpretation is stronger because the commit explicitly describes a second `kref_put()` on an already released queue, which is a lifetime corruption primitive and may become UAF-like. There is no demonstrated privilege escalation or controlled object reuse in the patch, so it should not be treated as proven code execution, but it is too strong to auto-close as ordinary Moderate. ## 5. One-sentence report phrase A race in the NVMe/TCP target ICReq path can let a remote host close the connection during queue teardown and cause a second `kref_put()` on an already released queue, leading to DoS and possible lifetime corruption. ## 6. Manual review recommendation **MANUAL CHECK REQUIRED** Manual review is required because this is a network-reachable storage target race with explicit released-queue reference misuse, making UAF or double-free style impact plausible even though exploitation beyond DoS is not demonstrated. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: nvmet-tcp: fix race between ICReq handling and queue teardown Commit: 49891c8fe0cb43fbbe480da1cdccfbbaeb820cb3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=49891c8fe0cb43fbbe480da1cdccfbbaeb820cb3 Commit description: nvmet_tcp_handle_icreq() updates queue->state after sending an Initialization Connection Response (ICResp), but it does so without serializing against target-side queue teardown. If an NVMe/TCP host sends an Initialization Connection Request (ICReq) and immediately closes the connection, target-side teardown may start in softirq context before io_work drains the already buffered ICReq. In that case, nvmet_tcp_schedule_release_queue() sets queue->state to NVMET_TCP_Q_DISCONNECTING and drops the queue reference under state_lock. If io_work later processes that ICReq, nvmet_tcp_handle_icreq() can still overwrite the state back to NVMET_TCP_Q_LIVE. That defeats the DISCONNECTING-state guard in nvmet_tcp_schedule_release_queue() and allows a later socket state change to re-enter teardown and issue a second kref_put() on an already released queue. The ICResp send failure path has the same problem. If teardown has already moved the queue to DISCONNECTING, a send error can still overwrite the state with NVMET_TCP_Q_FAILED, again reopening the window for a second teardown path to drop the queue reference. Fix this by serializing both post-send state transitions with state_lock and bailing out if teardown has already started. Use -ESHUTDOWN as an internal sentinel for that bail-out path rather than propagating it as a transport error like -ECONNRESET. Keep nvmet_tcp_socket_error() setting rcv_state to NVMET_TCP_RECV_ERR before honoring that sentinel so receive-side parsing stays quiesced until the existing release path completes. Fixes: c46a6465bac2 ("nvmet-tcp: add NVMe over TCP target driver") Cc: stable@vger.kernel.org Reported-by: Shivam Kumar Tested-by: Shivam Kumar Signed-off-by: Chaitanya Kulkarni Signed-off-by: Keith Busch Signed-off-by: Greg Kroah-Hartman Changed files: drivers/nvme/target/tcp.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=49891c8fe0cb43fbbe480da1cdccfbbaeb820cb3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46135 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46135 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:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/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: 7 Paranoid ActionableScore: 8 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).