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GHSA-88XJ-3P4J-2C73

Vulnerability from github – Published: 2026-10-23 15:31 – Updated: 2026-10-23 15:31

Details

In the Linux kernel, the following vulnerability has been resolved:

namespace: check a recursive bind mount for mount namespace loops

do_loopback() refuses to bind mount the file of a mount namespace that is as old as the caller's or older because a mount namespace that holds a mount of its own file, or of an ancestor's, would cause a cycle. But it only checks the dentry the bind mount starts from. With MS_REC everything below it is copied and do_loopback() passes CL_COPY_MNT_NS_FILE so mount namespace files below the source are copied.

That's fine for a source in the caller's own mount namespace. Every mount namespace file in there passed the same check when it was bind-mounted. It isn't fine for a source in another mount namespace. may_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter what mount namespace it lives in so that /proc//ns/ and pidfds can be bind mounted. If we create a bind-mount stack of mount namespaces file descriptors the kernel will copy them irrespective of their ancestoral relationship to the mount namespace in question:

151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw 152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw

Mount 152 is a mount of the mount namespace file of mount namespace 4026532293 inside mount namespace 4026532293. That namespace and every mount in it are leaked... All it takes is a process in an older mount namespace that stacks the file and repeating it leaks without limit:

after control: Shmem: 380 kB child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok after cycle: Shmem: 65916 kB

do_move_mount() runs check_for_nsfs_mounts() over a detached tree for exactly that reason. Do the same for the copy before it is grafted.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98989"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-23T13:17:20Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check a recursive bind mount for mount namespace loops\n\ndo_loopback() refuses to bind mount the file of a mount namespace that\nis as old as the caller\u0027s or older because a mount namespace that holds\na mount of its own file, or of an ancestor\u0027s, would cause a cycle. But\nit only checks the dentry the bind mount starts from. With MS_REC\neverything below it is copied and do_loopback() passes\nCL_COPY_MNT_NS_FILE so mount namespace files below the source are\ncopied.\n\nThat\u0027s fine for a source in the caller\u0027s own mount namespace. Every\nmount namespace file in there passed the same check when it was\nbind-mounted. It isn\u0027t fine for a source in another mount namespace.\nmay_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter\nwhat mount namespace it lives in so that /proc/\u003cpid\u003e/ns/\u003cns\u003e and pidfds\ncan be bind mounted. If we create a bind-mount stack of mount namespaces\nfile descriptors the kernel will copy them irrespective of their\nancestoral relationship to the mount namespace in question:\n\n  151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw\n  152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw\n\nMount 152 is a mount of the mount namespace file of mount namespace\n4026532293 inside mount namespace 4026532293. That namespace and every\nmount in it are leaked... All it takes is a process in an older mount\nnamespace that stacks the file and repeating it leaks without limit:\n\n  after control: Shmem:               380 kB\n  child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok\n  after cycle: Shmem:             65916 kB\n\ndo_move_mount() runs check_for_nsfs_mounts() over a detached tree for\nexactly that reason. Do the same for the copy before it is grafted.",
  "id": "GHSA-88xj-3p4j-2c73",
  "modified": "2026-10-23T15:31:34Z",
  "published": "2026-10-23T15:31:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98989"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/37a82f400efa4d263542a5fa41755b21057f1e5d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a0ba48256f5dff6f75a45f8ce39fe57f21df1022"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c640a01a78e42302879006ed7b7d5a9a943ba815"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98989 (GCVE-0-2026-98989)

Vulnerability from cvelistv5 – Published: 2026-10-23 12:20 – Updated: 2026-10-23 12:20

Title

namespace: check a recursive bind mount for mount namespace loops

Summary

In the Linux kernel, the following vulnerability has been resolved: namespace: check a recursive bind mount for mount namespace loops do_loopback() refuses to bind mount the file of a mount namespace that is as old as the caller's or older because a mount namespace that holds a mount of its own file, or of an ancestor's, would cause a cycle. But it only checks the dentry the bind mount starts from. With MS_REC everything below it is copied and do_loopback() passes CL_COPY_MNT_NS_FILE so mount namespace files below the source are copied. That's fine for a source in the caller's own mount namespace. Every mount namespace file in there passed the same check when it was bind-mounted. It isn't fine for a source in another mount namespace. may_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter what mount namespace it lives in so that /proc/<pid>/ns/<ns> and pidfds can be bind mounted. If we create a bind-mount stack of mount namespaces file descriptors the kernel will copy them irrespective of their ancestoral relationship to the mount namespace in question: 151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw 152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw Mount 152 is a mount of the mount namespace file of mount namespace 4026532293 inside mount namespace 4026532293. That namespace and every mount in it are leaked... All it takes is a process in an older mount namespace that stacks the file and repeating it leaks without limit: after control: Shmem: 380 kB child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok after cycle: Shmem: 65916 kB do_move_mount() runs check_for_nsfs_mounts() over a detached tree for exactly that reason. Do the same for the copy before it is grafted.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 7061 records in the last 180 days details

References

3 references

URL	Tags
https://git.kernel.org/stable/c/a0ba48256f5dff6f7…
https://git.kernel.org/stable/c/37a82f400efa4d263…
https://git.kernel.org/stable/c/c640a01a78e423028…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: e149ed2b805fefdccf7ccdfc19eca22fdd4514ac , < a0ba48256f5dff6f75a45f8ce39fe57f21df1022 (git) Affected: e149ed2b805fefdccf7ccdfc19eca22fdd4514ac , < 37a82f400efa4d263542a5fa41755b21057f1e5d (git) Affected: e149ed2b805fefdccf7ccdfc19eca22fdd4514ac , < c640a01a78e42302879006ed7b7d5a9a943ba815 (git)
Linux	Linux	Affected: 3.19 Unaffected: 0 , < 3.19 (semver) Unaffected: 6.18.57 , ≤ 6.18.* (semver) Unaffected: 7.2.11 , ≤ 7.2.* (semver) Unaffected: 7.3 , ≤ * (original_commit_for_fix)

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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
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          "programFiles": [
            "fs/namespace.c"
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          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "e149ed2b805fefdccf7ccdfc19eca22fdd4514ac",
              "versionType": "git"
            },
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              "lessThan": "37a82f400efa4d263542a5fa41755b21057f1e5d",
              "status": "affected",
              "version": "e149ed2b805fefdccf7ccdfc19eca22fdd4514ac",
              "versionType": "git"
            },
            {
              "lessThan": "c640a01a78e42302879006ed7b7d5a9a943ba815",
              "status": "affected",
              "version": "e149ed2b805fefdccf7ccdfc19eca22fdd4514ac",
              "versionType": "git"
            }
          ]
        },
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          "versions": [
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              "status": "affected",
              "version": "3.19"
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              "version": "0",
              "versionType": "semver"
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              "status": "unaffected",
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            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
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              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "3.19",
                  "vulnerable": true
                },
                {
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                }
              ],
              "negate": false,
              "operator": "OR"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check a recursive bind mount for mount namespace loops\n\ndo_loopback() refuses to bind mount the file of a mount namespace that\nis as old as the caller\u0027s or older because a mount namespace that holds\na mount of its own file, or of an ancestor\u0027s, would cause a cycle. But\nit only checks the dentry the bind mount starts from. With MS_REC\neverything below it is copied and do_loopback() passes\nCL_COPY_MNT_NS_FILE so mount namespace files below the source are\ncopied.\n\nThat\u0027s fine for a source in the caller\u0027s own mount namespace. Every\nmount namespace file in there passed the same check when it was\nbind-mounted. It isn\u0027t fine for a source in another mount namespace.\nmay_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter\nwhat mount namespace it lives in so that /proc/\u003cpid\u003e/ns/\u003cns\u003e and pidfds\ncan be bind mounted. If we create a bind-mount stack of mount namespaces\nfile descriptors the kernel will copy them irrespective of their\nancestoral relationship to the mount namespace in question:\n\n  151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw\n  152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw\n\nMount 152 is a mount of the mount namespace file of mount namespace\n4026532293 inside mount namespace 4026532293. That namespace and every\nmount in it are leaked... All it takes is a process in an older mount\nnamespace that stacks the file and repeating it leaks without limit:\n\n  after control: Shmem:               380 kB\n  child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok\n  after cycle: Shmem:             65916 kB\n\ndo_move_mount() runs check_for_nsfs_mounts() over a detached tree for\nexactly that reason. Do the same for the copy before it is grafted."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-10-23T12:20:08.366Z",
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    "datePublished": "2026-10-23T12:20:08.366Z",
    "dateReserved": "2026-09-25T10:25:14.384Z",
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    "state": "PUBLISHED"
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Sightings

Author	Source	Type	Date	Other

Nomenclature

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.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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