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

Vulnerability from cvelistv5 – Published: 2026-05-08 14:22 – Updated: 2026-05-11 22:25
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
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 741a295130606143edbf9fc740f633dbc1e6225f , < 845bf3c6963a52096d0d3866e4a92db77a0c03d8 (git)
Affected: 741a295130606143edbf9fc740f633dbc1e6225f , < d3ffc8f13034af895531a02c30b1fe3a34b46432 (git)
Affected: 741a295130606143edbf9fc740f633dbc1e6225f , < d0d99f60538ddb4a62ccaac2168d8f448965f083 (git)
Affected: 741a295130606143edbf9fc740f633dbc1e6225f , < d7963d6997fea86a6def242ac36198b86655f912 (git)
Affected: 741a295130606143edbf9fc740f633dbc1e6225f , < aa9ebc084505fb26dd90f4d7a249045aad152043 (git)
Affected: 741a295130606143edbf9fc740f633dbc1e6225f , < af8f4be3b68ac8caa41c8e5ead0eeaf5e85e42d0 (git)
Affected: 741a295130606143edbf9fc740f633dbc1e6225f , < 42e21e74061b0ebbd859839f81acf10efad02a27 (git)
Affected: 741a295130606143edbf9fc740f633dbc1e6225f , < 6c4b2243cb6c0755159bd567130d5e12e7b10d9f (git)
Create a notification for this product.
Linux Linux Affected: 2.6.16
Unaffected: 0 , < 2.6.16 (semver)
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)
Create a notification for this product.
Show details on NVD website
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          {
            "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) ;-/"
          }
        ],
        "id": "CVE-2026-43472",
        "lastModified": "2026-06-17T10:49:40.283",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 5.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 3.6,
              "source": "nvd@nist.gov",
              "type": "Primary"
            }
          ]
        },
        "published": "2026-05-08T15:17:00.313",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/42e21e74061b0ebbd859839f81acf10efad02a27"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/6c4b2243cb6c0755159bd567130d5e12e7b10d9f"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/845bf3c6963a52096d0d3866e4a92db77a0c03d8"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/aa9ebc084505fb26dd90f4d7a249045aad152043"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/af8f4be3b68ac8caa41c8e5ead0eeaf5e85e42d0"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/d0d99f60538ddb4a62ccaac2168d8f448965f083"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/d3ffc8f13034af895531a02c30b1fe3a34b46432"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/d7963d6997fea86a6def242ac36198b86655f912"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-908"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-02T19:37:43+00:00",
      "cve": "CVE-2026-43472",
      "id": "CVE-2026-43472",
      "initial_release_date": "2026-05-08T00:00:00+00:00",
      "product_status:known_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: unshare: fix unshare_fs() handling",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43472.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-10-01T01:16:55Z",
      "cve": "CVE-2026-43472",
      "id": "CVE-2026-43472",
      "initial_release_date": "2026-05-11T14:13:19Z",
      "product_status:known_affected": "645",
      "product_status:known_not_affected": "15",
      "product_status:recommended": "287",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-43472",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-43472.json",
      "version": "11"
    }
  }
}



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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

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.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.