{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-93810", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-18T17:59:28.790Z", "datePublished": "2026-09-24T16:02:46.426Z", "dateUpdated": "2026-10-03T10:57:42.502Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-03T10:57:42.502Z" }, "descriptions": [ { "lang": "en", "value": "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()." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7, "baseSeverity": "HIGH" }, "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/cachefiles/namei.c" ], "versions": [ { "version": "24a81759b65fa85767739999d91523691c5e2ea5", "lessThan": "e582a3e99584d5a634a3cbce4b12e9381fd5d964", "status": "affected", "versionType": "git" }, { "version": "24a81759b65fa85767739999d91523691c5e2ea5", "lessThan": "246098a2b8e88761e92cf82c1be1ec576437b176", "status": "affected", "versionType": "git" }, { "version": "24a81759b65fa85767739999d91523691c5e2ea5", "lessThan": "e9c2e68c3890a935abbd5f54dbce653f9a16836c", "status": "affected", "versionType": "git" }, { "version": "24a81759b65fa85767739999d91523691c5e2ea5", "lessThan": "90b306eee037d0a6a8f4aac834b46e05c5ddd0bf", "status": "affected", "versionType": "git" }, { "version": "24a81759b65fa85767739999d91523691c5e2ea5", "lessThan": "af6830cc12dfe86c832dccc9c9878a93aaa22f83", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/cachefiles/namei.c" ], "versions": [ { "version": "6.1", "status": "affected" }, { "version": "0", "lessThan": "6.1", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.189", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.158", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.111", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.53", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.1.189" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.6.158" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.12.111" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.18.53" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "7.2" } ] } ] } ], "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" } } } }