CVE-2026-53341 (GCVE-0-2026-53341)

Vulnerability from cvelistv5 – Published: 2026-07-01 13:32 – Updated: 2026-07-01 13:32
VLAI
Title
fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh()
Summary
In the Linux kernel, the following vulnerability has been resolved: fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh() may_decode_fh() accesses mount::mnt_ns without holding any locks; that means the mount can concurrently be unmounted, and the mnt_namespace can concurrently be freed after an RCU grace period. This race can happens as follows, assuming that the mount point was created by open_tree(..., OPEN_TREE_CLONE): thread 1 thread 2 RCU __do_sys_open_by_handle_at do_handle_open handle_to_path may_decode_fh is_mounted [mount::mnt_ns access] [mount::mnt_ns access] __do_sys_close fput_close_sync __fput dissolve_on_fput umount_tree class_namespace_excl_destructor namespace_unlock free_mnt_ns mnt_ns_tree_remove call_rcu(mnt_ns_release_rcu) mnt_ns_release_rcu mnt_ns_release kfree [mnt_namespace::user_ns access] **UAF** Fix it by taking rcu_read_lock() around the mount::mnt_ns access, like in __prepend_path(). Additionally, document the semantics of mount::mnt_ns, and use WRITE_ONCE() for writers that can race with lockless readers. This bug is unreachable unless one of the following is set: - CONFIG_PREEMPTION - CONFIG_RCU_STRICT_GRACE_PERIOD because it requires an RCU grace period to happen during a syscall without an explicit preemption. This doesn't seem to have interesting security impact; worst-case, it could leak the result of an integer comparison to userspace (from the level check in cap_capable()), cause an endless loop, or crash the kernel by dereferencing an invalid address.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 620c266f394932e5decc4b34683a75dfc59dc2f4 , < 32138633e51e6db59e474765cf93268c92b42888 (git)
Affected: 620c266f394932e5decc4b34683a75dfc59dc2f4 , < a8ed2c29fcfdac78db96c9da4e659c8a513f2a94 (git)
Affected: 620c266f394932e5decc4b34683a75dfc59dc2f4 , < 40ab6644b99685755f740b872c00ef40d9aa870e (git)
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Linux Linux Affected: 6.11
Unaffected: 0 , < 6.11 (semver)
Unaffected: 6.18.36 , ≤ 6.18.* (semver)
Unaffected: 7.0.13 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/fhandle.c",
            "fs/mount.h",
            "fs/namespace.c"
          ],
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          "vendor": "Linux",
          "versions": [
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              "version": "6.11"
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              "versionType": "semver"
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              "status": "unaffected",
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              "versionType": "semver"
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              "status": "unaffected",
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfhandle: fix UAF due to unlocked -\u003emnt_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\u0027t 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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-01T13:32:22.873Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/32138633e51e6db59e474765cf93268c92b42888"
        },
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          "url": "https://git.kernel.org/stable/c/a8ed2c29fcfdac78db96c9da4e659c8a513f2a94"
        },
        {
          "url": "https://git.kernel.org/stable/c/40ab6644b99685755f740b872c00ef40d9aa870e"
        }
      ],
      "title": "fhandle: fix UAF due to unlocked -\u003emnt_ns read in may_decode_fh()",
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  },
  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-53341",
    "datePublished": "2026-07-01T13:32:22.873Z",
    "dateReserved": "2026-06-09T07:44:35.399Z",
    "dateUpdated": "2026-07-01T13:32:22.873Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "date": "2026-07-02",
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      "percentile": "0.04975"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-53341\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-07-01T14:16:42.143\",\"lastModified\":\"2026-07-01T14:16:42.143\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nfhandle: fix UAF due to unlocked -\u003emnt_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\u0027t 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.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/fhandle.c\",\"fs/mount.h\",\"fs/namespace.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"620c266f394932e5decc4b34683a75dfc59dc2f4\",\"lessThan\":\"32138633e51e6db59e474765cf93268c92b42888\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"620c266f394932e5decc4b34683a75dfc59dc2f4\",\"lessThan\":\"a8ed2c29fcfdac78db96c9da4e659c8a513f2a94\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"620c266f394932e5decc4b34683a75dfc59dc2f4\",\"lessThan\":\"40ab6644b99685755f740b872c00ef40d9aa870e\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/fhandle.c\",\"fs/mount.h\",\"fs/namespace.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.11\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.11\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.36\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.13\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/32138633e51e6db59e474765cf93268c92b42888\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/40ab6644b99685755f740b872c00ef40d9aa870e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a8ed2c29fcfdac78db96c9da4e659c8a513f2a94\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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