From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64320][IMPORTANT] nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page Date: Sat, 25 Jul 2026 15:01:50 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64320 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 8 X-AL-KERNEL-ActionableScore-Lower: 7 X-AL-KERNEL-Commit: 33b974eb626154ae9348f2bac7de84cb2a3d9dd4 List-Id: CVE: CVE-2026-64320 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: NO Patch: nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page Commit: 33b974eb626154ae9348f2bac7de84cb2a3d9dd4 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=33b974eb626154ae9348f2bac7de84cb2a3d9dd4 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64320 Analysis date: Sat, 25 Jul 2026 15:01:50 -0400 ActionableScore: 8 ActionableScore lower bound: 7 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A pre-auth OOB heap read in the nvmet Discovery Get Log Page path lets a reachable NVMe fabric peer disclose kernel heap memory and potentially crash the target host. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64320 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64320 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-2026-64320 IMPORTANT CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H';CWE-125;*CWE-200;*CWE-20;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H';BEST CVSS score: '8.3';DESCR 'A pre-authentication out-of-bounds heap read exists in the NVMe target Discovery Get Log Page path because nvmet_execute_disc_get_log_page uses a host supplied 64 bit log page offset as buffer plus offset without validating it against the allocated discovery log page size. A fabric peer that can reach the NVMe target can request data starting past the end of the small kzalloc buffer and receive adjacent kernel heap contents back in the Get Log Page response. The same source side offset can also point the in-kernel copy at unmapped memory and crash or panic the target host. For the CVSS the PR:N is used because the Discovery controller is reachable before host authentication once a fabric peer can connect. AV:A is used because NVMe fabrics are normally deployed on isolated storage or data center networks rather than the public Internet. Impact includes high confidentiality loss due to kernel heap disclosure and high availability impact due to target kernel crash. Integrity impact is limited in the paranoid score because the leak can expose kernel pointers and support follow on exploitation analysis, but the patch does not show a direct write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) YES WRITE OOB INIT NVME LEAK LOG IMPROVEONLY KERNEL_PANIC_PLUS_UAF LINUS NO NO 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 Reachable by any TCP/RDMA/FC fabric peer that can connect to the NVMe target Discovery controller. This is pre-auth. * Reliable kernel crash / strong DoS: +1 An attacker-controlled offset can make the in-kernel memcpy read from unmapped memory and crash or panic the target host. * Confidentiality impact plausible: +1 The bug provides a concrete OOB heap read and returns adjacent kernel heap contents to the peer. The report states that a default nvmet-tcp loopback target leaked kernel pointers. * Availability impact realistic: +1 The crash path is direct and host-impacting, not only a local warning or recoverable protocol error. * Important filesystem/storage path: +1 This is in the NVMe target discovery path, a storage fabric control path. * Practical exploit behavior demonstrated or strongly implied: +1 The commit message gives a concrete pre-auth read pattern and empirical leakage results. * Rare / non-default exposure: -1 nvmet target service must be configured and reachable. This is not normally exposed to the public Internet. Paranoid additional signal: * Integrity impact follow-on concern: +1 Not a direct write primitive, but leaking kernel heap contents and canonical kernel pointers can materially assist follow-on exploitation in the same target environment. ## 3. Reachability analysis The bug is triggerable by a fabric peer that can reach the NVMe target Discovery controller. No NVMe host authentication is required for the Discovery subsystem, so PR is effectively none once network or fabric reachability exists. This is not a generic Internet-exposed kernel path. Realistic exposure is usually inside storage, data-center, RDMA, FC, or isolated NVMe/TCP networks. However, within that network boundary the trigger is straightforward and pre-auth. Namespaces and containers are not the main privilege boundary here. The relevant boundary is fabric reachability to an enabled nvmet target. Call-site confidence: high. The patch shows the exact unsafe source pointer `buffer + offset` passed to `nvmet_copy_to_sgl()`. ## 4. Severity interpretation This behaves more like an Important-class candidate than an ordinary Moderate. The issue is not merely a crash: it includes a concrete pre-auth kernel heap disclosure primitive plus a direct target crash path. Realistic exploitation evidence supports high confidentiality impact and strong DoS. There is no direct arbitrary write or proven privilege escalation primitive in the patch, so integrity impact should remain conservative in the main score, with only paranoid follow-on concern. ## 5. One-sentence report phrase A pre-auth OOB heap read in the nvmet Discovery Get Log Page path lets a reachable NVMe fabric peer disclose kernel heap memory and potentially crash the target host. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: pre-auth fabric reachability, confirmed kernel heap disclosure, kernel pointer leakage, and target crash behavior make this unsuitable for auto-closure even though the service is usually limited to storage networks. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page Commit: 33b974eb626154ae9348f2bac7de84cb2a3d9dd4 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=33b974eb626154ae9348f2bac7de84cb2a3d9dd4 Commit description: nvmet_execute_disc_get_log_page() validates only the dword alignment of the host-supplied Log Page Offset (lpo). The 64-bit offset is then added to a small kzalloc'd buffer that holds the discovery log page and the result is passed straight to nvmet_copy_to_sgl(), which memcpy()s data_len bytes out to the host with no source-side bound check: u64 offset = nvmet_get_log_page_offset(req->cmd); /* 64-bit host */ size_t data_len = nvmet_get_log_page_len(req->cmd); /* 32-bit host */ ... if (offset & 0x3) { ... } /* only check */ ... alloc_len = sizeof(*hdr) + entry_size * discovery_log_entries(req); buffer = kzalloc(alloc_len, GFP_KERNEL); ... status = nvmet_copy_to_sgl(req, 0, buffer + offset, data_len); The Discovery controller is unauthenticated -- nvmet_host_allowed() returns true unconditionally for the discovery subsystem -- so the call is reachable pre-authentication by any TCP/RDMA/FC peer that can reach the nvmet target. With a discovery log page of ~1 KiB, an attacker requesting up to 4 KiB starting at offset == alloc_len reads the next slab page out and gets its content returned over the fabric (an empirical run on a default nvmet-tcp loopback target leaked 81 canonical kernel pointers in one Get Log Page response). Pointing the offset at unmapped kernel memory faults the in-kernel memcpy and crashes (or panics, on panic_on_oops=1) the target host instead. The attacker-controlled source-side offset pattern "nvmet_copy_to_sgl(req, 0, buffer + ATTACKER_OFFSET, ...)" is unique to nvmet_execute_disc_get_log_page in the entire nvmet codebase: every other Get Log Page handler in admin-cmd.c either ignores lpo (and silently starts every response at offset 0) or tracks a local destination offset with a fixed source pointer. Validate the host-supplied offset against the log page size, cap the copy length to what is actually available, and zero-fill any remainder of the host transfer buffer. The zero-fill matches the existing short-response pattern in nvmet_execute_get_log_changed_ns() (admin-cmd.c) and prevents leaking transport SGL contents when the host asks for more bytes than the log page contains. Fixes: a07b497 ("nvmet: add a generic NVMe target") Cc: stable@vger.kernel.org Reviewed-by: Chaitanya Kulkarni Reviewed-by: Christoph Hellwig Signed-off-by: Bryam Vargas Signed-off-by: Keith Busch Signed-off-by: Greg Kroah-Hartman Changed files: drivers/nvme/target/discovery.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=33b974eb626154ae9348f2bac7de84cb2a3d9dd4 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64320 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64320 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:H/I:N/A:H The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H The Best / paranoid CVSS score: 8.3 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: NO 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).