From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89482][MODERATE 7.0] nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone Date: Fri, 11 Sep 2026 23:55:25 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89482 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: 7 X-AL-KERNEL-ActionableScore-Lower: 6 X-AL-KERNEL-Commit: b36161701cb366f416afdcf70771d432a7c74753 List-Id: CVE: CVE-2026-89482 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone Commit: b36161701cb366f416afdcf70771d432a7c74753 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b36161701cb366f416afdcf70771d432a7c74753 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89482 Analysis date: Fri, 11 Sep 2026 23:55:25 -0400 ActionableScore: 7 ActionableScore lower bound: 6 Actionable bucket: Strong Important candidate Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89482 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89482 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-2026-89482 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89482 CHECK WITH IMPACT FROM ORIG NN MODERATE 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-787;CWE-824;*CWE-20;CWE-703;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'A wild memory write in the NVMe/TCP host receive path can occur because C2HData validation used blk_rq_payload_bytes() without also checking the driver private request state. For WRITE_ZEROES, a request can have non zero bytes but no physical segments, leaving the current receive iterator uninitialized while stale iterator state from an earlier command on the same tag may still exist. A malicious or compromised NVMe/TCP target can send C2HData for this command state and cause nvme_tcp_recv_data to copy attacker supplied data into the stale iterator destination, resulting in memory corruption or a kernel crash. For the CVSS the PR:N is used because the attacker does not need local privileges on the victim host when acting as the remote NVMe/TCP target already used by the host. AV:A is used because NVMe/TCP is normally deployed on storage or data center networks rather than the public Internet. Impact is at least denial of service and data corruption. For the paranoid score, C:H/I:H/A:H is defensible because the bug is a kernel memory write through stale iterator state and should not be treated as DoS only.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate (with actual score 7) YES REMOTE KASAN INIT NVME NETWORK KERNEL_PANIC_PLUS_UAF HARDWARE LINUS TEST KPANIC KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=6 PrimitiveClass=CLASS_A RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 6 * Conservative score: 6. No floor or cap applied. * Raw paranoid score: 7 * Paranoid score: 7. No floor or cap applied. * Final recommended bucket: **Strong Important candidate**:: 2. Signal breakdown Conservative signals: * +2 Strong kernel corruption primitive. The patch and report establish a real write through a stale or uninitialized iterator in nvme_tcp_recv_data(), with KASAN reporting wild-memory-access in _copy_to_iter(). * +2 Network reachable from the peer role. A malicious or compromised NVMe/TCP target can send C2HData for a WRITE_ZEROES command state over an existing NVMe/TCP connection. * +1 Reliable kernel crash / strong DoS. The supplied trace shows KASAN wild-memory-access in the NVMe/TCP receive workqueue and supports kernel crash or fatal fault impact. * +1 Integrity plausible. The operation copies target-controlled C2HData into an unintended stale iterator destination, so corruption of host memory or host I/O buffers is plausible. Paranoid additional signal: * +1 Weak exploitation leverage concern. The attacker controls the received C2HData payload and can influence protocol sequencing and tag reuse from the target side, leaving unresolved exploitation leverage beyond a simple NULL dereference or crash-only fault. Non-awarded or withheld signals: * RealUAF not set. The evidence establishes stale iterator use and wild memory write, but not a direct object free followed by use of the freed object as a classic UAF. * Concrete repeated release/refcount not awarded. There is no first release followed by a second lifetime-mutating put/free/refcount operation on the same dangling reference. * Arbitrary write not awarded. The destination is stale iterator state from a previous command/tag, not a demonstrated attacker-selected arbitrary kernel address. * Controlled reclaim not demonstrated. * Confidentiality not awarded. No read-back or disclosure path is established. * Extra Availability not awarded. The same crash is already counted once. * Race/timing penalty not applied. This is a protocol state validation failure, not a narrow timing race. * Rare subsystem penalty not applied. NVMe/TCP is specialized storage networking, but the vulnerable path is a normal receive path once the feature is deployed. 3. Reachability analysis The evaluated attacker is a malicious or compromised NVMe/TCP target, or an attacker able to impersonate or tamper with the target side of an existing NVMe/TCP connection. The vulnerable host receives C2HData from that target in the NVMe/TCP host receive path. No local host-admin privileges are required by that attacker once the victim host is connected to the target. The attack does depend on the victim using NVMe/TCP and having an established or attacker-influenced target connection. This is a deployment prerequisite, not evidence that the attacker must have host administrator privileges on the victim. Namespace-scoped privilege is not relevant to the supplied trigger. This is not a local namespace capability path. The issue is not normally public Internet exposed. NVMe/TCP deployments are typically storage or data-center network deployments. Practical exploitation usually requires access to that storage network, control of the target endpoint, or compromise of a target already trusted by the host. No special rare hardware is established. No narrow race is required. The state requirement is specific: a WRITE_ZEROES request can have nonzero bytes but no physical segments, leaving req->iter untouched while C2HData is still accepted based on blk_rq_payload_bytes() alone. 4. Primitive and severity interpretation The exact primitive is a stale iterator based memory write in the NVMe/TCP host receive path. The receive gate accepted C2HData based only on blk_rq_payload_bytes(rq). For REQ_OP_WRITE_ZEROES, the request may have nonzero request bytes but no physical segments, so setup does not initialize the iterator for the current command. The receive path can then copy target-controlled data into whatever iterator state remained from a previous command on the same tag. This is active stale state in an I/O data path, not a fixed harmless metadata mismatch. The demonstrated consequence is wild-memory-access and likely kernel crash. The stronger unresolved consequence is corruption of unintended host memory or I/O buffers. The patch-supported evidence does not prove arbitrary read/write, controlled reclaim, credential corruption, or privilege escalation, but it does establish a concrete kernel write primitive with attacker-controlled data. PrimitiveClass is CLASS_A because a real attacker-influenced kernel memory write is established. RealUAF is NO because the supplied evidence does not directly establish classic use-after-free. ImportantCandidate is YES because the bug is not crash-only and involves target-controlled data being written through stale host-side iterator state. AutoDowngradeAllowed is NO because automatic Moderate downgrading would discard an established memory corruption primitive with unresolved exploitation leverage. Operationally, this is a Strong Important candidate for systems using NVMe/TCP host connections to untrusted, compromised, or attacker-reachable targets. It is less broadly exposed than an Internet-facing network service, but it should not be treated as ordinary DoS. 5. One-sentence report phrase A malicious or compromised NVMe/TCP target can send C2HData for a WRITE_ZEROES command state and cause the host to copy attacker-controlled data through stale iterator state, leading to kernel memory corruption or crash. 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch establishes a concrete kernel memory write through stale iterator state with attacker-controlled network payload from the NVMe/TCP target side. Arbitrary write and LPE are not proven, but the primitive is stronger than crash-only DoS. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone Commit: b36161701cb366f416afdcf70771d432a7c74753 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b36161701cb366f416afdcf70771d432a7c74753 Commit description: Commit 25e5cb7 ("nvme-tcp: fix possible crash in write_zeroes processing") established that blk_rq_payload_bytes() must not be read without first checking blk_rq_nr_phys_segments(), and recorded the result in nvme_tcp_setup_cmd_pdu() as req->data_len. The receive side was left as it was. The two differ for REQ_OP_WRITE_ZEROES, which has no physical segments but a non-zero blk_rq_bytes(), so setup leaves req->iter untouched while the receive gate lets a C2HData through and nvme_tcp_recv_data() copies into whatever the previous command on that tag left there. The driver-private area is zeroed only when the tag set is allocated. Reproduced with a test target that leaves a residual iterator on a tag and then sends a C2HData for a WRITE_ZEROES command on the same tag: BUG: KASAN: wild-memory-access in _copy_to_iter+0x642/0x1330 Write of size 512 at addr ffe728c2175dfa81 by task kworker/0:1H/103 CPU: 0 UID: 0 PID: 103 Comm: kworker/0:1H Not tainted 7.2.0-rc5-NVMETCP-gf5098b6bae76 #1 PREEMPT(lazy) Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: nvme_tcp_wq nvme_tcp_io_work Call Trace: dump_stack_lvl+0x53/0x70 kasan_report+0xce/0x100 ? _copy_to_iter+0x642/0x1330 kasan_check_range+0x105/0x1b0 __asan_memcpy+0x3c/0x60 _copy_to_iter+0x642/0x1330 ? __pfx_sock_has_perm+0x10/0x10 ? worker_thread+0x45b/0xd10 ? __pfx__copy_to_iter+0x10/0x10 ? _raw_spin_lock_bh+0x83/0xe0 ? __pfx__raw_spin_lock_bh+0x10/0x10 __skb_datagram_iter+0xf3/0x820 ? __pfx_simple_copy_to_iter+0x10/0x10 ? __asan_memcpy+0x3c/0x60 ? skb_copy_bits+0x58d/0x830 skb_copy_datagram_iter+0x37/0x120 nvme_tcp_recv_skb+0xa07/0x4320 ? __pfx_nvme_tcp_recv_skb+0x10/0x10 __tcp_read_sock+0x1ab/0x810 ? __pfx_nvme_tcp_recv_skb+0x10/0x10 ? __pfx_lock_sock_nested+0x10/0x10 ? __pfx___tcp_read_sock+0x10/0x10 nvme_tcp_try_recv+0x152/0x1e0 ? __pfx_nvme_tcp_try_recv+0x10/0x10 ? __pfx_mutex_unlock+0x10/0x10 nvme_tcp_io_work+0x1e4/0x6c0 ? __schedule+0x181a/0x49f0 ? __pfx_nvme_tcp_io_work+0x10/0x10 process_one_work+0x633/0x1030 Keep the blk_rq_payload_bytes() test and add req->data_len to it. The old test is what rejects a C2HData naming a tag that is no longer in flight, because blk_update_request() zeroes rq->__data_len on completion; req->data_len and req->curr_bio are driver-private and survive completion, so they cannot stand in for it. Setup initialises the iterator only when both req->curr_bio and req->data_len are set, so the gate now tests the same two. Fixes: 25e5cb7 ("nvme-tcp: fix possible crash in write_zeroes processing") Cc: stable@vger.kernel.org Signed-off-by: Yehyeong Lee Signed-off-by: Keith Busch Signed-off-by: Greg Kroah-Hartman Changed files: drivers/nvme/host/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=b36161701cb366f416afdcf70771d432a7c74753 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89482 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89482 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:L/I:L/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: 6 Paranoid ActionableScore: 7 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).