{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-64398 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-64398 is a high-severity missing authorization vulnerability in Linux kernel, published on 25 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-64398 and fix it if it is affected.\n\nWhat it is: CVE-2026-64398 is a high-severity missing authorization vulnerability in Linux kernel, published on 25 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-64398 in the wild and no public exploit code.\n\nAffected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-64398/ (Markdown: https://insights.sbomify.com/CVE-2026-64398/index.md)","id":"CVE-2026-64398","markdown":"https://insights.sbomify.com/CVE-2026-64398/index.md","name":"CVE-2026-64398","record":{"aliases":["BELL-CVE-2026-64398","DEBIAN-CVE-2026-64398","GHSA-ch49-xqcg-99vv","ROOT-OS-DEBIAN-12-CVE-2026-64398","ROOT-OS-UBUNTU-2204-CVE-2026-64398","UBUNTU-CVE-2026-64398"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["data_modify"],"network_reachable":"yes","non_default_config":false,"product_category":"Linux kernel SMB server","requires_auth":"low_privilege","summary":"An authenticated SMB client can zero file data without FILE_WRITE_DATA permission due to a missing per-handle access check in ksmbd.","user_interaction":"not_required","vuln_class":"missing_authorization"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[{"product":"linux_kernel","vendor":"linux"}],"cvss":{"score":8.1,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H","version":"3.1"},"cwes":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: add a permission check for FSCTL_SET_ZERO_DATA\n\nFSCTL_SET_ZERO_DATA in smb2_ioctl() destroys file data via\nksmbd_vfs_zero_data() -\u003e vfs_fallocate(PUNCH_HOLE/ZERO_RANGE) after\nchecking only the share-level KSMBD_TREE_CONN_FLAG_WRITABLE, with no\nper-handle access check. A handle opened with only FILE_WRITE_ATTRIBUTES\nstill yields an FMODE_WRITE filp (FILE_WRITE_ATTRIBUTES is part of\nFILE_WRITE_DESIRE_ACCESS_LE, so smb2_create_open_flags() opens it\nO_WRONLY), so the vfs_fallocate FMODE_WRITE check does not stop it; only\nthe missing fp-\u003edaccess gate would. Reproduced on mainline 7.1-rc7 with\nKASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle\nzeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to\n(6/6; a FILE_READ_DATA-only handle was correctly denied).\n\nThis is the unfixed sibling of commit cc57232cae23 (\"ksmbd: fix FSCTL\npermission bypass by adding a permission check for FSCTL_SET_SPARSE\").\nBecause SET_ZERO_DATA writes data (not an attribute), require\nFILE_WRITE_DATA.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"ksmbd: add a permission check for FSCTL_SET_ZERO_DATA","id":"CVE-2026-64398","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"missing_authorization","year":"2026"},"n_packages":0,"n_references":6,"next":{"headline":"ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE","id":"CVE-2026-64399"},"packages":[],"prev":{"headline":"ksmbd: serialize QUERY_DIRECTORY requests per file","id":"CVE-2026-64397"},"products":["Linux"],"published":"2026-07-25","related":[{"cvss_score":8.8,"headline":"Linux Kernel Out-of-Bounds Write","id":"CVE-2026-53266","kev_date_added":"2026-09-18","published":"2026-06-25"},{"cvss_score":8.8,"headline":"Linux Kernel Improper Input Validation","id":"CVE-2013-6282","kev_date_added":"2022-09-15","published":"2013-11-19"},{"cvss_score":8.4,"headline":"Linux Kernel Heap-Based Buffer Overflow","id":"CVE-2022-0185","kev_date_added":"2024-08-21","published":"2022-02-11"},{"cvss_score":8.4,"headline":"Linux Kernel Privilege Escalation","id":"CVE-2013-2094","kev_date_added":"2022-09-15","published":"2013-05-14"},{"cvss_score":7.8,"headline":"Linux Kernel Unspecified","id":"CVE-2026-53362","kev_date_added":"2026-08-27","published":"2026-07-04"},{"cvss_score":7.8,"headline":"Linux Kernel Missing Initialization of a Variable","id":"CVE-2026-46300","kev_date_added":"2026-10-28","published":"2026-05-23"},{"cvss_score":7.8,"headline":"Linux Kernel Race Condition","id":"CVE-2025-39964","kev_date_added":"2026-09-18","published":"2025-10-13"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-08-17","vendors":["Linux"]},"summary":"An authenticated SMB client can zero file data without FILE_WRITE_DATA permission due to a missing per-handle access check in ksmbd.","url":"https://insights.sbomify.com/CVE-2026-64398/"}