{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-53341", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-06-09T07:44:35.399Z", "datePublished": "2026-07-01T13:32:22.873Z", "dateUpdated": "2026-08-05T12:35:02.388Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:35:02.388Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh()\n\nmay_decode_fh() accesses mount::mnt_ns without holding any locks; that\nmeans the mount can concurrently be unmounted, and the mnt_namespace can\nconcurrently be freed after an RCU grace period.\n\nThis race can happens as follows, assuming that the mount point was\ncreated by open_tree(..., OPEN_TREE_CLONE):\n\nthread 1 thread 2 RCU\n __do_sys_open_by_handle_at\n do_handle_open\n handle_to_path\n may_decode_fh\n is_mounted\n [mount::mnt_ns access]\n [mount::mnt_ns access]\n__do_sys_close\n fput_close_sync\n __fput\n dissolve_on_fput\n umount_tree\n class_namespace_excl_destructor\n namespace_unlock\n free_mnt_ns\n mnt_ns_tree_remove\n call_rcu(mnt_ns_release_rcu)\n mnt_ns_release_rcu\n mnt_ns_release\n kfree\n [mnt_namespace::user_ns access] **UAF**\n\nFix it by taking rcu_read_lock() around the mount::mnt_ns access, like\nin __prepend_path().\nAdditionally, document the semantics of mount::mnt_ns, and use WRITE_ONCE()\nfor writers that can race with lockless readers.\n\nThis bug is unreachable unless one of the following is set:\n\n - CONFIG_PREEMPTION\n - CONFIG_RCU_STRICT_GRACE_PERIOD\n\nbecause it requires an RCU grace period to happen during a syscall without\nan explicit preemption.\n\nThis doesn't seem to have interesting security impact; worst-case, it could\nleak the result of an integer comparison to userspace (from the level\ncheck in cap_capable()), cause an endless loop, or crash the kernel by\ndereferencing an invalid address." } ], "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 vulnerable code is reached through local syscalls, primarily `open_by_handle_at()` racing with close/fput of a mount file created by `open_tree(..., OPEN_TREE_CLONE)`. There is no network or adjacent attack path.\nAC:L - The attacker can control both sides of the race by running concurrent local threads that call `open_by_handle_at()` and close the cloned mount file. Although the bug requires preemption or strict RCU grace periods, those are reasonable kernel configurations and the race is attacker-driven.\nPR:L - The path requires namespace-relative capabilities such as `CAP_SYS_ADMIN` and `CAP_DAC_READ_SEARCH`, which an unprivileged local user can obtain inside a user namespace on systems where unprivileged user namespaces are enabled. It does not require real init-namespace root.\nUI:N - No victim action is required; the attacker directly invokes the relevant syscalls and controls the racing threads. The mount clone, handle input, and close operation are all attacker initiated.\nS:U - The vulnerability affects kernel VFS/mount namespace state within the same security authority. It is a local kernel memory-safety issue, not a VM escape or cross-scope boundary bypass.\nC:H - The bug is a kernel use-after-free of `struct mnt_namespace`, followed by dereferencing reclaimed memory through `mnt_ns->user_ns` and capability-walk fields. Per the higher-severity rule for kernel UAFs, this is scored as high confidentiality impact.\nI:H - The immediate operation is a stale read in an authorization check, but reclaimed kernel heap contents can influence capability-check control flow and UAFs are treated as potentially exploitable memory corruption. Under the required uncertainty rule, integrity impact is high.\nA:H - The stale `mnt_namespace` dereference can crash the kernel, loop indefinitely, or otherwise destabilize the system. A local attacker can repeatedly trigger the race, so availability impact is high." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/fhandle.c", "fs/mount.h", "fs/namespace.c" ], "versions": [ { "version": "620c266f394932e5decc4b34683a75dfc59dc2f4", "lessThan": "15ea8dc42a02259d49dee38a658d40f60fcd75ed", "status": "affected", "versionType": "git" }, { "version": "620c266f394932e5decc4b34683a75dfc59dc2f4", "lessThan": "32138633e51e6db59e474765cf93268c92b42888", "status": "affected", "versionType": "git" }, { "version": "620c266f394932e5decc4b34683a75dfc59dc2f4", "lessThan": "a8ed2c29fcfdac78db96c9da4e659c8a513f2a94", "status": "affected", "versionType": "git" }, { "version": "620c266f394932e5decc4b34683a75dfc59dc2f4", "lessThan": "40ab6644b99685755f740b872c00ef40d9aa870e", "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/fhandle.c", "fs/mount.h", "fs/namespace.c" ], "versions": [ { "version": "6.11", "status": "affected" }, { "version": "0", "lessThan": "6.11", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.95", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.36", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.13", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "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": "6.11", "versionEndExcluding": "6.12.95" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.18.36" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "7.0.13" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/15ea8dc42a02259d49dee38a658d40f60fcd75ed" }, { "url": "https://git.kernel.org/stable/c/32138633e51e6db59e474765cf93268c92b42888" }, { "url": "https://git.kernel.org/stable/c/a8ed2c29fcfdac78db96c9da4e659c8a513f2a94" }, { "url": "https://git.kernel.org/stable/c/40ab6644b99685755f740b872c00ef40d9aa870e" } ], "title": "fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh()", "x_generator": { "engine": "bippy-1.2.0" } } } }