{"api_version":"1","generated_at":"2026-10-27T05:12:01+00:00","cve":"CVE-2026-93810","urls":{"html":"https://cve.report/CVE-2026-93810","api":"https://cve.report/api/cve/CVE-2026-93810.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-93810","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-93810"},"summary":{"title":"cachefiles: Fix double fput","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: Fix double fput\n\nFix a double fput() in error handling in cachefiles_create_tmpfile().","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-24 17:17:14","updated_at":"2026-10-03 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the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: Fix double fput\n\nFix a double fput() in error handling in cachefiles_create_tmpfile()."}],"metrics":[{"cvssV3_1":{"baseScore":7,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:L - The extra fput is in cachefiles_create_tmpfile(), reached from nfs_fscache_open_file() (or CIFS/9p/AFS/Ceph fscache_use_cookie()) → fscache_perform_lookup() → cachefiles_lookup_cookie() → cachefiles_look_up_object() → cachefiles_create_file(), or from cachefiles_invalidate_cookie(); a local open/inval of an fscache-backed file is the entry, not a remote protocol message.\nAC:H - The double fput runs only when kernel_tmpfile_open()'s file has a NULL f_op->read_iter or f_op->write_iter. cachefiles_add_cache() requires tmpfile/xattr/sync_fs and s_blocksize<=PAGE_SIZE but never checks those f_ops; the only in-tree tmpfile FS lacking write_iter is hugetlbfs, which add_cache rejects, so an attacker cannot make a bound ext4/xfs/btrfs/f2fs tmpfile take this branch.\nPR:L - nfs_fscache_open_file() and the sibling fscache_use_cookie() open paths have no capable() check, so an unprivileged user with read access on an already-bound cachefiles/fscache mount drives cookie lookup into cachefiles_create_tmpfile(); cachefiles_daemon_open() needs init-namespace CAP_SYS_ADMIN, but that is not this trigger.\nUI:N - The attacker themselves open or invalidate files on the fscache-enabled netfs mount, which queues fscache_perform_lookup() into cachefiles_create_tmpfile(); no other user must mount the volume or issue cachefilesd commands.\nS:U - Double-putting the cache tmpfile's struct file corrupts host kernel file-refcount and filp_cachep state only; it does not cross a KVM/Xen, IOMMU, or other distinct authority.\nC:H - On the !read_iter/!write_iter branch, cachefiles_create_tmpfile() fput()s then err_unuse calls file_inode(file) and fput()s again. fscache_perform_lookup() runs in a PF_KTHREAD worker so the first put is deferred via delayed_fput_work; a later file_inode() on that pointer is a UAF read of a SLAB_TYPESAFE_BY_RCU struct file.\nI:H - The leftover fput before goto err_unuse is a struct-file double-put: if delayed __fput() has already file_free()'d the tmpfile, the second file_ref_put() writes a recycled filp_cachep object (or an underflowed live ref into the dead zone), a UAF write primitive against struct file.\nA:H - The second put hits __file_ref_put_badval()'s \"imbalanced put on file reference count\" WARN_ONCE, and if delayed_fput already ran, file_inode()/inode_lock/fput in cachefiles_create_tmpfile() err_unuse dereference freed memory and oops the fscache worker."}]}],"providerMetadata":{"dateUpdated":"2026-10-03T10:57:42.502Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/e582a3e99584d5a634a3cbce4b12e9381fd5d964"},{"url":"https://git.kernel.org/stable/c/246098a2b8e88761e92cf82c1be1ec576437b176"},{"url":"https://git.kernel.org/stable/c/e9c2e68c3890a935abbd5f54dbce653f9a16836c"},{"url":"https://git.kernel.org/stable/c/90b306eee037d0a6a8f4aac834b46e05c5ddd0bf"},{"url":"https://git.kernel.org/stable/c/af6830cc12dfe86c832dccc9c9878a93aaa22f83"}],"title":"cachefiles: Fix double fput","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-93810","datePublished":"2026-09-24T16:02:46.426Z","dateReserved":"2026-09-18T17:59:28.790Z","dateUpdated":"2026-10-03T10:57:42.502Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-24 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double fput"}]}}}