GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

CVE-2026-74343 (GCVE-0-2026-74343)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:58 – Updated: 2026-08-17 05:46
VLAI
Title
kernfs: fix xattr race condition with multiple superblocks
Summary
In the Linux kernel, the following vulnerability has been resolved: kernfs: fix xattr race condition with multiple superblocks Multiple superblocks with different namespaces can share the same kernfs_node when kernfs_test_super() finds a matching root but different namespace. This means multiple inodes from different superblocks can reference the same kernfs_node->iattr->xattrs structure. The VFS layer only holds per-inode locks during xattr operations, which is insufficient to serialize concurrent xattr modifications on the shared kernfs_node. This can lead to race conditions in simple_xattr_set() where the lookup->replace/remove sequence is not atomic with respect to operations from other superblocks. Fix this by protecting xattr operations with the existing hashed kernfs_locks->open_file_mutex[] array, which is already used to protect per-node open file data. The hashed mutex array provides scalable per-node serialization (scaled by CPU count, up to 1024 locks on 32+ CPU systems) with zero memory overhead. Changes: - Rename open_file_mutex[] to node_mutex[] to reflect dual purpose - Add kernfs_node_lock_ptr() and kernfs_node_lock() helpers - Protect simple_xattr_set() calls in kernfs_xattr_set() and kernfs_vfs_user_xattr_set() with the hashed mutex - Update file.c to use new helpers via compatibility wrappers - Update documentation to explain the extended lock usage
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b32c4a213698ab351b44da2fd1b2a5976c7fa033 , < bf53db51359939755084d08156684ed649489592 (git)
Affected: b32c4a213698ab351b44da2fd1b2a5976c7fa033 , < 6a07814ff643b5c8e1353d8c6229f52fde205cde (git)
guessed Create a notification for this product.
Linux Linux Affected: 7.1
Unaffected: 0 , < 7.1 (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/kernfs/file.c",
            "fs/kernfs/inode.c",
            "fs/kernfs/kernfs-internal.h",
            "fs/kernfs/mount.c",
            "include/linux/kernfs.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "bf53db51359939755084d08156684ed649489592",
              "status": "affected",
              "version": "b32c4a213698ab351b44da2fd1b2a5976c7fa033",
              "versionType": "git"
            },
            {
              "lessThan": "6a07814ff643b5c8e1353d8c6229f52fde205cde",
              "status": "affected",
              "version": "b32c4a213698ab351b44da2fd1b2a5976c7fa033",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/kernfs/file.c",
            "fs/kernfs/inode.c",
            "fs/kernfs/kernfs-internal.h",
            "fs/kernfs/mount.c",
            "include/linux/kernfs.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.5",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nkernfs: fix xattr race condition with multiple superblocks\n\nMultiple superblocks with different namespaces can share the same\nkernfs_node when kernfs_test_super() finds a matching root but\ndifferent namespace. This means multiple inodes from different\nsuperblocks can reference the same kernfs_node-\u003eiattr-\u003exattrs\nstructure.\n\nThe VFS layer only holds per-inode locks during xattr operations,\nwhich is insufficient to serialize concurrent xattr modifications on\nthe shared kernfs_node. This can lead to race conditions in\nsimple_xattr_set() where the lookup-\u003ereplace/remove sequence is not\natomic with respect to operations from other superblocks.\n\nFix this by protecting xattr operations with the existing hashed\nkernfs_locks-\u003eopen_file_mutex[] array, which is already used to\nprotect per-node open file data. The hashed mutex array provides\nscalable per-node serialization (scaled by CPU count, up to 1024 locks\non 32+ CPU systems) with zero memory overhead.\n\nChanges:\n- Rename open_file_mutex[] to node_mutex[] to reflect dual purpose\n- Add kernfs_node_lock_ptr() and kernfs_node_lock() helpers\n- Protect simple_xattr_set() calls in kernfs_xattr_set() and\n  kernfs_vfs_user_xattr_set() with the hashed mutex\n- Update file.c to use new helpers via compatibility wrappers\n- Update documentation to explain the extended lock usage"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached only through local VFS xattr operations (setxattr/fsetxattr syscalls) on kernfs-backed mounts such as cgroup2 and sysfs; there is no network-facing handler or remote pre-auth path to the vulnerable code.\nAC:L - The attacker fully controls both racing threads by mounting the same kernfs hierarchy from different namespace-tagged superblocks (e.g. sysfs in two network namespaces) and issuing concurrent setxattr calls against the same shared kernfs_node.\nPR:L - Exploitation requires only local user capabilities obtainable in an unprivileged user namespace (CAP_SYS_ADMIN to create namespaces and mount cgroup2/sysfs), not init-namespace root or host administrator privileges.\nUI:N - No victim interaction is required; the attacker mounts the filesystems, selects the target kernfs_node, and triggers the race with their own concurrent setxattr operations.\nS:U - Impact is confined to kernel memory corruption and privilege escalation within the same kernel/host security boundary; this is not a VM escape, sandbox breakout, or cross-authority scope change.\nC:H - Concurrent unsynchronized simple_xattr_set() on a shared rhashtable/list can cause use-after-free and heap corruption, which is readily weaponizable for arbitrary kernel memory disclosure, not merely a bounded leak.\nI:H - The race corrupts shared xattr rhashtable and list structures, enabling use-after-free and heap metadata corruption that can be leveraged for arbitrary kernel writes and local privilege escalation/code execution.\nA:H - The race can trigger kernel oops/panic from list/rhashtable corruption or use-after-free during concurrent replace/remove/free paths, causing complete loss of kernel availability even without full exploitation."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:46:08.382Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/bf53db51359939755084d08156684ed649489592"
        },
        {
          "url": "https://git.kernel.org/stable/c/6a07814ff643b5c8e1353d8c6229f52fde205cde"
        }
      ],
      "title": "kernfs: fix xattr race condition with multiple superblocks",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74343",
    "datePublished": "2026-08-15T05:58:32.577Z",
    "dateReserved": "2026-08-15T05:44:03.886Z",
    "dateUpdated": "2026-08-17T05:46:08.382Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-74343",
      "date": "2026-09-04",
      "epss": "0.0012",
      "percentile": "0.02081"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-74343\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-15T06:22:35.370\",\"lastModified\":\"2026-08-17T06:19:28.850\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nkernfs: fix xattr race condition with multiple superblocks\\n\\nMultiple superblocks with different namespaces can share the same\\nkernfs_node when kernfs_test_super() finds a matching root but\\ndifferent namespace. This means multiple inodes from different\\nsuperblocks can reference the same kernfs_node-\u003eiattr-\u003exattrs\\nstructure.\\n\\nThe VFS layer only holds per-inode locks during xattr operations,\\nwhich is insufficient to serialize concurrent xattr modifications on\\nthe shared kernfs_node. This can lead to race conditions in\\nsimple_xattr_set() where the lookup-\u003ereplace/remove sequence is not\\natomic with respect to operations from other superblocks.\\n\\nFix this by protecting xattr operations with the existing hashed\\nkernfs_locks-\u003eopen_file_mutex[] array, which is already used to\\nprotect per-node open file data. The hashed mutex array provides\\nscalable per-node serialization (scaled by CPU count, up to 1024 locks\\non 32+ CPU systems) with zero memory overhead.\\n\\nChanges:\\n- Rename open_file_mutex[] to node_mutex[] to reflect dual purpose\\n- Add kernfs_node_lock_ptr() and kernfs_node_lock() helpers\\n- Protect simple_xattr_set() calls in kernfs_xattr_set() and\\n  kernfs_vfs_user_xattr_set() with the hashed mutex\\n- Update file.c to use new helpers via compatibility wrappers\\n- Update documentation to explain the extended lock usage\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/kernfs/file.c\",\"fs/kernfs/inode.c\",\"fs/kernfs/kernfs-internal.h\",\"fs/kernfs/mount.c\",\"include/linux/kernfs.h\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"b32c4a213698ab351b44da2fd1b2a5976c7fa033\",\"lessThan\":\"bf53db51359939755084d08156684ed649489592\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b32c4a213698ab351b44da2fd1b2a5976c7fa033\",\"lessThan\":\"6a07814ff643b5c8e1353d8c6229f52fde205cde\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/kernfs/file.c\",\"fs/kernfs/inode.c\",\"fs/kernfs/kernfs-internal.h\",\"fs/kernfs/mount.c\",\"include/linux/kernfs.h\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"7.1\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"7.1\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.5\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/6a07814ff643b5c8e1353d8c6229f52fde205cde\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/bf53db51359939755084d08156684ed649489592\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-20T20:52:51+00:00",
      "cve": "CVE-2026-74343",
      "id": "CVE-2026-74343",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: kernfs: fix xattr race condition with multiple superblocks",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74343.json",
      "version": "3"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.