CVE-2026-43472 (GCVE-0-2026-43472)

Vulnerability from cvelistv5 – Published: 2026-05-08 14:22 – Updated: 2026-05-08 14:22
VLAI?
Title
unshare: fix unshare_fs() handling
Summary
In the Linux kernel, the following vulnerability has been resolved: unshare: fix unshare_fs() handling There's an unpleasant corner case in unshare(2), when we have a CLONE_NEWNS in flags and current->fs hadn't been shared at all; in that case copy_mnt_ns() gets passed current->fs instead of a private copy, which causes interesting warts in proof of correctness] > I guess if private means fs->users == 1, the condition could still be true. Unfortunately, it's worse than just a convoluted proof of correctness. Consider the case when we have CLONE_NEWCGROUP in addition to CLONE_NEWNS (and current->fs->users == 1). We pass current->fs to copy_mnt_ns(), all right. Suppose it succeeds and flips current->fs->{pwd,root} to corresponding locations in the new namespace. Now we proceed to copy_cgroup_ns(), which fails (e.g. with -ENOMEM). We call put_mnt_ns() on the namespace created by copy_mnt_ns(), it's destroyed and its mount tree is dissolved, but... current->fs->root and current->fs->pwd are both left pointing to now detached mounts. They are pinning those, so it's not a UAF, but it leaves the calling process with unshare(2) failing with -ENOMEM _and_ leaving it with pwd and root on detached isolated mounts. The last part is clearly a bug. There is other fun related to that mess (races with pivot_root(), including the one between pivot_root() and fork(), of all things), but this one is easy to isolate and fix - treat CLONE_NEWNS as "allocate a new fs_struct even if it hadn't been shared in the first place". Sure, we could go for something like "if both CLONE_NEWNS *and* one of the things that might end up failing after copy_mnt_ns() call in create_new_namespaces() are set, force allocation of new fs_struct", but let's keep it simple - the cost of copy_fs_struct() is trivial. Another benefit is that copy_mnt_ns() with CLONE_NEWNS *always* gets a freshly allocated fs_struct, yet to be attached to anything. That seriously simplifies the analysis... FWIW, that bug had been there since the introduction of unshare(2) ;-/
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 845bf3c6963a52096d0d3866e4a92db77a0c03d8 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d3ffc8f13034af895531a02c30b1fe3a34b46432 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d0d99f60538ddb4a62ccaac2168d8f448965f083 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d7963d6997fea86a6def242ac36198b86655f912 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < aa9ebc084505fb26dd90f4d7a249045aad152043 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < af8f4be3b68ac8caa41c8e5ead0eeaf5e85e42d0 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 42e21e74061b0ebbd859839f81acf10efad02a27 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 6c4b2243cb6c0755159bd567130d5e12e7b10d9f (git)
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    Linux Linux Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.78 , ≤ 6.12.* (semver)
Unaffected: 6.18.19 , ≤ 6.18.* (semver)
Unaffected: 6.19.9 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "product": "Linux",
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              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.167",
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              "lessThanOrEqual": "6.6.*",
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.78",
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              "lessThanOrEqual": "6.18.*",
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              "status": "unaffected",
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nunshare: fix unshare_fs() handling\n\nThere\u0027s an unpleasant corner case in unshare(2), when we have a\nCLONE_NEWNS in flags and current-\u003efs hadn\u0027t been shared at all; in that\ncase copy_mnt_ns() gets passed current-\u003efs instead of a private copy,\nwhich causes interesting warts in proof of correctness]\n\n\u003e I guess if private means fs-\u003eusers == 1, the condition could still be true.\n\nUnfortunately, it\u0027s worse than just a convoluted proof of correctness.\nConsider the case when we have CLONE_NEWCGROUP in addition to CLONE_NEWNS\n(and current-\u003efs-\u003eusers == 1).\n\nWe pass current-\u003efs to copy_mnt_ns(), all right.  Suppose it succeeds and\nflips current-\u003efs-\u003e{pwd,root} to corresponding locations in the new namespace.\nNow we proceed to copy_cgroup_ns(), which fails (e.g. with -ENOMEM).\nWe call put_mnt_ns() on the namespace created by copy_mnt_ns(), it\u0027s\ndestroyed and its mount tree is dissolved, but...  current-\u003efs-\u003eroot and\ncurrent-\u003efs-\u003epwd are both left pointing to now detached mounts.\n\nThey are pinning those, so it\u0027s not a UAF, but it leaves the calling\nprocess with unshare(2) failing with -ENOMEM _and_ leaving it with\npwd and root on detached isolated mounts.  The last part is clearly a bug.\n\nThere is other fun related to that mess (races with pivot_root(), including\nthe one between pivot_root() and fork(), of all things), but this one\nis easy to isolate and fix - treat CLONE_NEWNS as \"allocate a new\nfs_struct even if it hadn\u0027t been shared in the first place\".  Sure, we could\ngo for something like \"if both CLONE_NEWNS *and* one of the things that might\nend up failing after copy_mnt_ns() call in create_new_namespaces() are set,\nforce allocation of new fs_struct\", but let\u0027s keep it simple - the cost\nof copy_fs_struct() is trivial.\n\nAnother benefit is that copy_mnt_ns() with CLONE_NEWNS *always* gets\na freshly allocated fs_struct, yet to be attached to anything.  That\nseriously simplifies the analysis...\n\nFWIW, that bug had been there since the introduction of unshare(2) ;-/"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-08T14:22:31.556Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/845bf3c6963a52096d0d3866e4a92db77a0c03d8"
        },
        {
          "url": "https://git.kernel.org/stable/c/d3ffc8f13034af895531a02c30b1fe3a34b46432"
        },
        {
          "url": "https://git.kernel.org/stable/c/d0d99f60538ddb4a62ccaac2168d8f448965f083"
        },
        {
          "url": "https://git.kernel.org/stable/c/d7963d6997fea86a6def242ac36198b86655f912"
        },
        {
          "url": "https://git.kernel.org/stable/c/aa9ebc084505fb26dd90f4d7a249045aad152043"
        },
        {
          "url": "https://git.kernel.org/stable/c/af8f4be3b68ac8caa41c8e5ead0eeaf5e85e42d0"
        },
        {
          "url": "https://git.kernel.org/stable/c/42e21e74061b0ebbd859839f81acf10efad02a27"
        },
        {
          "url": "https://git.kernel.org/stable/c/6c4b2243cb6c0755159bd567130d5e12e7b10d9f"
        }
      ],
      "title": "unshare: fix unshare_fs() handling",
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43472",
    "datePublished": "2026-05-08T14:22:31.556Z",
    "dateReserved": "2026-05-01T14:12:56.011Z",
    "dateUpdated": "2026-05-08T14:22:31.556Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-43472\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-08T15:17:00.313\",\"lastModified\":\"2026-05-08T15:17:00.313\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nunshare: fix unshare_fs() handling\\n\\nThere\u0027s an unpleasant corner case in unshare(2), when we have a\\nCLONE_NEWNS in flags and current-\u003efs hadn\u0027t been shared at all; in that\\ncase copy_mnt_ns() gets passed current-\u003efs instead of a private copy,\\nwhich causes interesting warts in proof of correctness]\\n\\n\u003e I guess if private means fs-\u003eusers == 1, the condition could still be true.\\n\\nUnfortunately, it\u0027s worse than just a convoluted proof of correctness.\\nConsider the case when we have CLONE_NEWCGROUP in addition to CLONE_NEWNS\\n(and current-\u003efs-\u003eusers == 1).\\n\\nWe pass current-\u003efs to copy_mnt_ns(), all right.  Suppose it succeeds and\\nflips current-\u003efs-\u003e{pwd,root} to corresponding locations in the new namespace.\\nNow we proceed to copy_cgroup_ns(), which fails (e.g. with -ENOMEM).\\nWe call put_mnt_ns() on the namespace created by copy_mnt_ns(), it\u0027s\\ndestroyed and its mount tree is dissolved, but...  current-\u003efs-\u003eroot and\\ncurrent-\u003efs-\u003epwd are both left pointing to now detached mounts.\\n\\nThey are pinning those, so it\u0027s not a UAF, but it leaves the calling\\nprocess with unshare(2) failing with -ENOMEM _and_ leaving it with\\npwd and root on detached isolated mounts.  The last part is clearly a bug.\\n\\nThere is other fun related to that mess (races with pivot_root(), including\\nthe one between pivot_root() and fork(), of all things), but this one\\nis easy to isolate and fix - treat CLONE_NEWNS as \\\"allocate a new\\nfs_struct even if it hadn\u0027t been shared in the first place\\\".  Sure, we could\\ngo for something like \\\"if both CLONE_NEWNS *and* one of the things that might\\nend up failing after copy_mnt_ns() call in create_new_namespaces() are set,\\nforce allocation of new fs_struct\\\", but let\u0027s keep it simple - the cost\\nof copy_fs_struct() is trivial.\\n\\nAnother benefit is that copy_mnt_ns() with CLONE_NEWNS *always* gets\\na freshly allocated fs_struct, yet to be attached to anything.  That\\nseriously simplifies the analysis...\\n\\nFWIW, that bug had been there since the introduction of unshare(2) ;-/\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/42e21e74061b0ebbd859839f81acf10efad02a27\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6c4b2243cb6c0755159bd567130d5e12e7b10d9f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/845bf3c6963a52096d0d3866e4a92db77a0c03d8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/aa9ebc084505fb26dd90f4d7a249045aad152043\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/af8f4be3b68ac8caa41c8e5ead0eeaf5e85e42d0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d0d99f60538ddb4a62ccaac2168d8f448965f083\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d3ffc8f13034af895531a02c30b1fe3a34b46432\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d7963d6997fea86a6def242ac36198b86655f912\",\"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.

Sightings

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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.



Detection rules are retrieved from Rulezet.