From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89680][MODERATE 7.0] nfsd: fix nfsd_file leak on inter-server COPY setup failure Date: Sat, 12 Sep 2026 03:53:41 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89680 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: 3 X-AL-KERNEL-Commit: 1a6a41b848455bf6ba2c9da2dfb0730e608ce7ab List-Id: CVE: CVE-2026-89680 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: nfsd: fix nfsd_file leak on inter-server COPY setup failure Commit: 1a6a41b848455bf6ba2c9da2dfb0730e608ce7ab Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a6a41b848455bf6ba2c9da2dfb0730e608ce7ab Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89680 Analysis date: Sat, 12 Sep 2026 03:53:41 -0400 ActionableScore: 4 ActionableScore lower bound: 3 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-2026-89680 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89680 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-2026-89680 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89680 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'An nfsd resource leak can occur when nfsd4_setup_inter_ssc fails during an NFSv4 COPY operation. The error path returned directly and skipped the common cleanup path, leaving an nfsd_file reference held and pinning related file, inode, dentry, and vfsmount objects. For the CVSS the PR:L is used because practical triggering normally requires a client that can access the NFS service and issue COPY operations against an allowed export or session. The issue is network reachable through nfsd, but it depends on the inter-server COPY path and a setup failure, so AC:H is used. Impact is denial of service through cumulative resource exhaustion. No direct confidentiality or integrity impact is assigned because the observed primitive is a reference leak, not UAF, OOB access, info leak, or arbitrary write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) YES DISK SIMPLEFIX LEAK NETWORK KPANIC YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 3 * Conservative score: 3. No floor or cap applied. * Raw paranoid score: 4 * Paranoid score: 4. No floor or cap applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Conservative positive signals: * +2 Remote reachable / directly network-triggerable: the vulnerable path is in nfsd handling of NFSv4 COPY, reachable through network NFS requests by a client that can access the service and relevant export/session. * +1 Concrete persistent kernel resource/reference leak: failed inter-server COPY setup skips the common cleanup path and leaks one nfsd_file reference, pinning file, inode, dentry, and vfsmount objects. Paranoid additional signal: * +1 Availability/resource exhaustion concern: repeated failed inter-server COPY attempts can accumulate pinned kernel objects and may eventually cause meaningful resource exhaustion. Non-awarded signals: * RealUAF not awarded: the evidence shows a missing release/reference leak, not a stale post-free use. * Class A or Class B corruption not awarded: no UAF, double free, OOB access, arbitrary write, controlled reclaim, refcount takeover, or type confusion is established. * Reliable kernel crash not awarded conservatively: the patch establishes cumulative leaking/pinning, not an immediate kernel panic. * Confidentiality and integrity not awarded: the primitive is a resource/reference leak, not disclosure or unauthorized modification. * Strong LPE or weak LPE concern not awarded: no exploitation primitive beyond resource exhaustion is established. * Concrete repeated release/refcount mutation not awarded: the bug is missing release, not a second release through a dangling reference. * Extra Availability not double-counted beyond the paranoid sustained-exhaustion interpretation. * No negative privilege penalty applied: host-admin-equivalent privilege is not required by the supplied evidence for a remote NFS client to exercise the server-side COPY path. 3. Reachability analysis The likely attacker is a remote NFS client that can connect to the nfsd service and issue NFSv4 COPY operations against an allowed export or session. This is not an unauthenticated Internet-wide assumption, because practical triggering depends on NFS access control, valid protocol state, and the inter-server COPY path. However, it also does not require host administrator privileges on the victim server. HostAdminRequired is NO because the vulnerable operation is a server-side network protocol path and the attacker model is a client with NFS access, not a local host administrator. NamespaceScopedPrivilege is NO because the supplied evidence does not involve namespace-scoped capabilities. Prior host setup exists only in the ordinary sense that nfsd and the relevant NFSv4 inter-server COPY functionality must be configured and reachable. No special hardware, race timing, UAF timing window, or boot-only prerequisite is established. 4. Primitive and severity interpretation The exact primitive is a persistent reference leak. nfs4_preprocess_stateid_op takes a reference associated with nf_dst, and the failing inter-server COPY setup path returned directly instead of reaching the shared out cleanup path where release_copy_files would drop that reference. Each failed operation can therefore pin an nfsd_file and related VFS objects. This is not active structured UAF, not fixed stale storage, and not a repeated release/refcount corruption case. The demonstrated consequence is cumulative resource consumption and potential denial of service. The speculative consequence is broader resource exhaustion after repeated triggering, but there is no evidence of memory corruption, information disclosure, privilege escalation, or arbitrary kernel read/write. PrimitiveClass is CLASS_C because the established behavior is DoS/resource exhaustion without an independently useful corruption primitive. ImportantCandidate is NO because this is a resource leak without unresolved memory-corruption or authorization-boundary leverage. AutoDowngradeAllowed is YES because no Class A or strong Class B primitive remains unresolved, although network exposure makes manual review recommended before closure in environments where NFS is broadly reachable. Likely operational severity is low to moderate. It is more actionable than a purely local leak because it is in a network server path, but it does not rise to Important-class without evidence of rapid host-wide exhaustion, isolation bypass, or memory corruption. 5. One-sentence report phrase A failed NFSv4 inter-server COPY setup can skip nfsd cleanup and leak an nfsd_file reference, allowing an authorized remote NFS client to cause cumulative resource exhaustion and potential denial of service. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the bug is network reachable in NFS deployments and can leak persistent kernel/VFS references repeatedly, but the established primitive is resource exhaustion only and does not show UAF, memory corruption, privilege escalation, or data disclosure. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: nfsd: fix nfsd_file leak on inter-server COPY setup failure Commit: 1a6a41b848455bf6ba2c9da2dfb0730e608ce7ab Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a6a41b848455bf6ba2c9da2dfb0730e608ce7ab Commit description: When nfsd4_setup_inter_ssc() fails, nfsd4_copy() returns nfserr_offload_denied directly, bypassing the out: label where release_copy_files() would drop the nf_dst reference taken by nfs4_preprocess_stateid_op(). Each failed inter-server COPY leaks one nfsd_file, pinning file/inode/dentry/vfsmount. Fix by setting status and jumping to out: instead of returning directly. Fixes: ce0887a ("NFSD add nfs4 inter ssc to nfsd4_copy") Cc: stable@vger.kernel.org Assisted-by: kres:claude-opus-4-7 Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20260531-nfsd-testing-v1-3-7bfa481b0540@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman Changed files: fs/nfsd/nfs4proc.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=1a6a41b848455bf6ba2c9da2dfb0730e608ce7ab ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89680 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89680 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:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.3 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: 3 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).