{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98982", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.384Z", "datePublished": "2026-10-23T12:19:59.784Z", "dateUpdated": "2026-10-24T14:09:50.745Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:09:50.745Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: don't let a pseudo dentry become the root of a mount\n\nd_alloc_pseudo() hands out dentries for pipes, sockets and other files\nthat are never anyone's child or parent. They carry DCACHE_NORCU and\ndentry_free() frees them right away because no lockless path walk can\never reach them. That holds as long as such a dentry isn't the root of\na mount. But bind mounting /proc/self/fd/ of such a file does\nexactly that.\n\nMost callers of alloc_file_pseudo() put their files on kernel-internal\nmounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It\nplaces the token file on the bpffs mount the caller handed it and that\nmount is in the caller's mount namespace so the clone goes through:\n\n mount --bind /proc/self/fd/ \n open_tree(tokfd, \"\", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount()\n\n__follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq\nand d_flags of the dentry and only then checks mount_lock. The dentry\ncan be gone by then. The final mntput() of an unmounted parent unhooks\na child that stayed attached to it under mount_lock alone. When the\nchild's holder does the final put right after that the root is dput()\nand freed immediately while a walker that found the mount hashed still\nlooks at it.\n\nRefuse to clone a mount with a DCACHE_NORCU dentry as its root. Nothing\nsensible can be done with a bind mount of a bpf token anyway." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Local bpf(BPF_TOKEN_CREATE) reaches bpf_token_create()/alloc_file_pseudo(), after which mount(MS_BIND) or open_tree(OPEN_TREE_CLONE) reaches the patched __do_loopback() on /proc/self/fd/; no network protocol carries the triggering data.\nAC:L - The attacker controls creation and teardown of the token-root mount and can race cleanup_mnt()/dput() against openat() reaching __follow_mount_rcu() using concurrent threads; neither side of the race requires external timing or victim-controlled state.\nPR:L - bpf_token_create() requires CAP_BPF in the bpffs user namespace, while open_tree(OPEN_TREE_CLONE) and move_mount() require CAP_SYS_ADMIN over the mount namespace; because bpf_fs_type has FS_USERNS_MOUNT, an ordinary user can obtain these capabilities through unprivileged user and mount namespaces.\nUI:N - The attacking process performs every required action itself: mounting delegated bpffs, creating the token, cloning and tearing down mounts, and racing openat(); no victim must mount, open, or otherwise process attacker-supplied data.\nS:U - The freed dentry is consumed by __follow_mount_rcu() inside the same host kernel, yielding ordinary local kernel compromise or denial of service rather than crossing a VM, IOMMU, or separate security-authority boundary.\nC:H - cleanup_mnt() can dput() and immediately free the DCACHE_NORCU mount root while __follow_mount_rcu() still reads its d_seq, d_flags, and potentially d_op; attacker-driven dentry-cache reuse makes this kernel UAF capable of high-impact memory disclosure.\nI:H - The freed struct dentry can be reclaimed through attacker-driven dentry allocation, letting heap spraying influence fields and the d_op->d_manage dispatch consumed by __follow_mount_rcu(); this is an exploitable kernel UAF path to arbitrary modification or control-flow hijacking.\nA:H - __follow_mount_rcu() dereferences the mount root after dentry_free() has returned it immediately to dentry_cache, so poisoned or reclaimed contents can cause a kernel oops or panic, and attacker-controlled threads can repeat the race." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/namespace.c" ], "versions": [ { "version": "35f96de04127d332a5c5e8a155d31f452f88c76d", "lessThan": "a256e31e0c54c4c37d2523aa52faabdcdd2ebc07", "status": "affected", "versionType": "git" }, { "version": "35f96de04127d332a5c5e8a155d31f452f88c76d", "lessThan": "7e1c466011ba9e64d43075396badc03191bcee44", "status": "affected", "versionType": "git" }, { "version": "35f96de04127d332a5c5e8a155d31f452f88c76d", "lessThan": "00287afa7cd989efdbf5822b7efac33cce7d489a", "status": "affected", "versionType": "git" }, { "version": "35f96de04127d332a5c5e8a155d31f452f88c76d", "lessThan": "b138e16fb1e81376cea89f727dda7bfccd140de4", "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/namespace.c" ], "versions": [ { "version": "6.9", "status": "affected" }, { "version": "0", "lessThan": "6.9", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.113", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.57", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.11", "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": "6.9", "versionEndExcluding": "6.12.113" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.18.57" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "7.2.11" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a256e31e0c54c4c37d2523aa52faabdcdd2ebc07" }, { "url": "https://git.kernel.org/stable/c/7e1c466011ba9e64d43075396badc03191bcee44" }, { "url": "https://git.kernel.org/stable/c/00287afa7cd989efdbf5822b7efac33cce7d489a" }, { "url": "https://git.kernel.org/stable/c/b138e16fb1e81376cea89f727dda7bfccd140de4" } ], "title": "namespace: don't let a pseudo dentry become the root of a mount", "x_generator": { "engine": "bippy-1.2.0" } } } }