{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-99180",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2026-09-25T10:25:14.399Z",
        "datePublished": "2026-10-28T10:35:33.578Z",
        "dateUpdated": "2026-10-28T10:35:33.578Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-10-28T10:35:33.578Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nunicode: free the map after a grace period\n\ngeneric_ci_d_hash() and generic_ci_d_compare() read sb->s_encoding and\ndereference the unicode map while a pathwalk in rcu mode holds nothing\nbut rcu_read_lock(). The filesystems that use them, ext4, f2fs and\ntmpfs, drop the map with utf8_unload() from ->put_super(), which runs\nwhen the last reference to the mount goes away. A lookup that is still\ninside such a filesystem at that point reads a freed map.\n\nWith a pathwalk held up in utf8_casefold_hash() while the last reference\nto a casefolded tmpfs goes away:\n\n  BUG: KASAN: slab-use-after-free in utf8nlookup+0x74c/0x950\n  Read of size 8 at addr ff110001030fe658 by task walker/98\n  Call Trace:\n   <TASK>\n   utf8nlookup+0x74c/0x950\n   utf8byte+0x160/0x1560\n   utf8_casefold_hash+0x167/0x230\n   generic_ci_d_hash+0xdd/0x1c0\n   link_path_walk+0x11ad/0x1d30\n   path_lookupat+0x63/0xb00\n   filename_lookup+0x1f1/0x5b0\n   vfs_statx+0xd7/0x3b0\n  [...]\n  Allocated by task 94:\n   __kmalloc_cache_noprof+0x249/0x560\n   utf8_load+0x4e/0x570\n   shmem_parse_opt_casefold.isra.0+0x92/0x270\n  [...]\n  Freed by task 97:\n   kfree+0x1db/0x5b0\n   shmem_put_super+0x72/0x170\n   generic_shutdown_super+0x14c/0x530\n   kill_anon_super+0x3a/0x60\n   deactivate_locked_super+0x9c/0xf0\n   cleanup_mnt+0x9f/0x130\n\nSo far that has been hard to hit. umount(2) waits for a grace period\nin namespace_unlock() before it drops the mount, so only a mount whose\nlast reference goes away elsewhere, like the close of a file or a chdir\nout of a lazily unmounted directory, can race a walker. So it is\nreachable.\n\nDelay the free until a grace period has passed. The map and the data\ntable it holds a reference to then outlive any pathwalk that found the\nsuperblock before the mount went away. The reference on the data table\nmodule is dropped from the rcu callback as well. utf8-core is built in\nwhenever CONFIG_UNICODE is set, so there is no module exit that would\nhave to wait for the callbacks.\n\nOverlayfs points the s_encoding of an overlay at the map of its first\nlayer without taking a reference of its own. That stays correct. The\nlayer is held by the overlay, so its map is dropped only after the\noverlay is gone."
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/unicode/utf8-core.c",
                        "include/linux/unicode.h"
                    ],
                    "versions": [
                        {
                            "version": "b886ee3e778ec2ad43e276fd378ab492cf6819b7",
                            "lessThan": "2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "b886ee3e778ec2ad43e276fd378ab492cf6819b7",
                            "lessThan": "6560c3d9a6925e3747d9ad8463e16010c31ba715",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "b886ee3e778ec2ad43e276fd378ab492cf6819b7",
                            "lessThan": "a96c5299bd7305eb984377681eb3222a57376405",
                            "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/unicode/utf8-core.c",
                        "include/linux/unicode.h"
                    ],
                    "versions": [
                        {
                            "version": "5.2",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "5.2",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.59",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2.13",
                            "lessThanOrEqual": "7.2.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.3",
                            "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": "5.2",
                                    "versionEndExcluding": "6.18.59"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "5.2",
                                    "versionEndExcluding": "7.2.13"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "5.2",
                                    "versionEndExcluding": "7.3"
                                }
                            ]
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8"
                },
                {
                    "url": "https://git.kernel.org/stable/c/6560c3d9a6925e3747d9ad8463e16010c31ba715"
                },
                {
                    "url": "https://git.kernel.org/stable/c/a96c5299bd7305eb984377681eb3222a57376405"
                }
            ],
            "title": "unicode: free the map after a grace period",
            "x_generator": {
                "engine": "bippy-1.2.0"
            }
        }
    }
}