{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39717","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T07:20:57.117Z","datePublished":"2025-09-05T17:21:24.528Z","dateUpdated":"2026-08-05T12:04:48.428Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:04:48.428Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nopen_tree_attr: do not allow id-mapping changes without OPEN_TREE_CLONE\n\nAs described in commit 7a54947e727b ('Merge patch series \"fs: allow\nchanging idmappings\"'), open_tree_attr(2) was necessary in order to\nallow for a detached mount to be created and have its idmappings changed\nwithout the risk of any racing threads operating on it. For this reason,\nmount_setattr(2) still does not allow for id-mappings to be changed.\n\nHowever, there was a bug in commit 2462651ffa76 (\"fs: allow changing\nidmappings\") which allowed users to bypass this restriction by calling\nopen_tree_attr(2) *without* OPEN_TREE_CLONE.\n\ncan_idmap_mount() prevented this bug from allowing an attached\nmountpoint's id-mapping from being modified (thanks to an is_anon_ns()\ncheck), but this still allows for detached (but visible) mounts to have\ntheir be id-mapping changed. This risks the same UAF and locking issues\nas described in the merge commit, and was likely unintentional."}],"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 - The vulnerability is reached purely through local syscalls — `open_tree(2)` to create a detached mount and `open_tree_attr(2)` to replace its idmapping. There is no remote or adjacent-network path to fs/namespace.c mount attribute handling.\nAC:L - The attacker controls both sides of the race entirely: one thread calls `open_tree_attr()` to free the old `struct mnt_idmap` while attacker-spawned threads hammer `openat()`/`statx()`/`open_tree(OPEN_TREE_CLONE)` on the same detached-mount fd, and the replace can be repeated in a loop with a heap spray of the kmalloc-cg-192 slab.\nPR:L - Only an unprivileged local user is required — `unshare -Urm` grants CAP_SYS_ADMIN over both the new mount namespace (satisfying `may_mount()`) and over the superblock's `s_user_ns` (satisfying `can_idmap_mount()`) for a self-mounted tmpfs or fuse filesystem, both of which carry `FS_USERNS_MOUNT | FS_ALLOW_IDMAP`.\nUI:N - The attacker performs every step — creating the detached mount, applying the first idmapping, and racing the replacement — within its own processes. No victim action of any kind is needed.\nS:U - The freed object and all corrupted state live in the kernel's own memory; the impact is confined to the kernel security authority with no crossing of a VM, IOMMU, or hypervisor boundary.\nC:H - This is a use-after-free on a heap object whose contents directly determine mapped uid/gid values, so refilling the freed slot lets the attacker forge `uid_gid_map.forward` into an arbitrary kernel pointer that `bsearch()` dereferences, with the result observable via `stat()` — an arbitrary kernel memory read.\nI:H - `clone_mnt()`'s `mnt_idmap_get()` performs a `refcount_inc()` on the freed object, giving a write primitive into reclaimed heap memory, and the stale/forged idmapping also causes ownership and permission decisions to be made from attacker-influenced data.\nA:H - Dereferencing the freed `struct mnt_idmap` and its `kfree()`d extent arrays, plus refcount underflow and double-free on repeated replacement, reliably produce an oops or panic taking down the whole system."}]}],"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":"2462651ffa76b87f9c2e4403ef6e6b89b703fb2f","lessThan":"69dbdc711d9130136824e3830191a6afffa0a1f0","status":"affected","versionType":"git"},{"version":"2462651ffa76b87f9c2e4403ef6e6b89b703fb2f","lessThan":"9308366f062129d52e0ee3f7a019f7dd41db33df","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":"6.15","status":"affected"},{"version":"0","lessThan":"6.15","status":"unaffected","versionType":"semver"},{"version":"6.16.4","lessThanOrEqual":"6.16.*","status":"unaffected","versionType":"semver"},{"version":"6.17","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":"6.15","versionEndExcluding":"6.16.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.17"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/69dbdc711d9130136824e3830191a6afffa0a1f0"},{"url":"https://git.kernel.org/stable/c/9308366f062129d52e0ee3f7a019f7dd41db33df"}],"title":"open_tree_attr: do not allow id-mapping changes without OPEN_TREE_CLONE","x_generator":{"engine":"bippy-1.2.0"}}}}