CVE-2025-40190 (GCVE-0-2025-40190)
Vulnerability from cvelistv5
Published
2025-11-12 21:56
Modified
2026-08-05 12:08
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ext4: guard against EA inode refcount underflow in xattr update syzkaller found a path where ext4_xattr_inode_update_ref() reads an EA inode refcount that is already <= 0 and then applies ref_change (often -1). That lets the refcount underflow and we proceed with a bogus value, triggering errors like: EXT4-fs error: EA inode <n> ref underflow: ref_count=-1 ref_change=-1 EXT4-fs warning: ea_inode dec ref err=-117 Make the invariant explicit: if the current refcount is non-positive, treat this as on-disk corruption, emit ext4_error_inode(), and fail the operation with -EFSCORRUPTED instead of updating the refcount. Delete the WARN_ONCE() as negative refcounts are now impossible; keep error reporting in ext4_error_inode(). This prevents the underflow and the follow-on orphan/cleanup churn.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 0   ≤
Version: 0   ≤
Version: 0   ≤
Version: 0   ≤
Version: 0   ≤
Version: 0   ≤
Version: 0   ≤
Create a notification for this product.
Show details on NVD website

To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/xattr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "ea39e712c2f5ae148ee5515798ae03523673e002",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "1cfb3e4ddbdc8e02e637b8852540bd4718bf4814",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "505e69f76ac497e788f4ea0267826ec7266b40c8",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "3d6269028246f4484bfed403c947a114bb583631",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "79ea7f3e11effe1bd9e753172981d9029133a278",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "6b879c4c6bbaab03c0ad2a983953bd1410bb165e",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "440b003f449a4ff2a00b08c8eab9ba5cd28f3943",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "57295e835408d8d425bef58da5253465db3d6888",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "5.4.301",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "5.10.246",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "5.15.195",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "6.1.157",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "6.6.113",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "6.12.54",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "6.17.4",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/xattr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThanOrEqual": "5.4.*",
              "status": "unaffected",
              "version": "5.4.301",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.246",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.195",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.113",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.54",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.4.301",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.246",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.195",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.157",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.113",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.54",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17.4",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: guard against EA inode refcount underflow in xattr update\n\nsyzkaller found a path where ext4_xattr_inode_update_ref() reads an EA\ninode refcount that is already \u003c= 0 and then applies ref_change (often\n-1). That lets the refcount underflow and we proceed with a bogus value,\ntriggering errors like:\n\n  EXT4-fs error: EA inode \u003cn\u003e ref underflow: ref_count=-1 ref_change=-1\n  EXT4-fs warning: ea_inode dec ref err=-117\n\nMake the invariant explicit: if the current refcount is non-positive,\ntreat this as on-disk corruption, emit ext4_error_inode(), and fail the\noperation with -EFSCORRUPTED instead of updating the refcount. Delete the\nWARN_ONCE() as negative refcounts are now impossible; keep error reporting\nin ext4_error_inode().\n\nThis prevents the underflow and the follow-on orphan/cleanup churn."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is triggered when the kernel parses an attacker-crafted ext4 image, reached locally through mount (USB automount via udisks2, a loop-mounted image file, or a container/appliance filesystem image). ext4 lacks FS_USERNS_MOUNT so there is no remote or namespace-based path \u2014 the malicious data must be presented to a local block device.\nAC:L - The attacker fully controls the on-disk EA inode\u0027s ctime/i_version fields that encode the refcount, so setting it to 0 or negative and forcing a decrement is deterministic; syzbot has a reliable C reproducer that fires during mount-time orphan cleanup with no race or memory-layout dependency.\nPR:N - The attacker needs no account or privileges on the target system \u2014 they only supply the crafted filesystem image (e.g. a USB stick or downloaded disk image); the mount is performed by the victim\u0027s automounter or administrator.\nUI:R - A user or automounter on the victim system must mount the attacker-supplied ext4 image for the corrupted EA inode refcount to be parsed.\nS:U - The underflow, the resulting WARN/panic, and the filesystem-metadata corruption are all confined to the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The underflow lets an EA inode be orphaned and freed while other inodes\u0027 xattr entries still reference it, so its inode number and data blocks are reallocated and later served through getxattr \u2014 and the Lustre-style path in ext4_xattr_inode_iget() bypasses ext4_xattr_inode_verify_hashes() entirely, allowing another file\u0027s contents to be disclosed.\nI:H - A bogus refcount (e.g. 0xFFFFFFFFFFFFFFFF) is written back to disk and clear_nlink()+ext4_orphan_add() is applied to an inode with i_nlink=2, deleting an inode that still has live directory entries and xattr references; ext4_xattr_inode_dec_ref_all() then decrements refcounts on reallocated inodes without hash validation, corrupting unrelated files\u0027 metadata and quota accounting.\nA:H - The path hits WARN_ONCE() in ext4_xattr_inode_update_ref(), which is a kernel panic under the widely deployed panic_on_warn setting, and the subsequent ext4 error either panics with errors=panic or forces the filesystem read-only, denying service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:08:26.693Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ea39e712c2f5ae148ee5515798ae03523673e002"
        },
        {
          "url": "https://git.kernel.org/stable/c/1cfb3e4ddbdc8e02e637b8852540bd4718bf4814"
        },
        {
          "url": "https://git.kernel.org/stable/c/505e69f76ac497e788f4ea0267826ec7266b40c8"
        },
        {
          "url": "https://git.kernel.org/stable/c/3d6269028246f4484bfed403c947a114bb583631"
        },
        {
          "url": "https://git.kernel.org/stable/c/79ea7f3e11effe1bd9e753172981d9029133a278"
        },
        {
          "url": "https://git.kernel.org/stable/c/6b879c4c6bbaab03c0ad2a983953bd1410bb165e"
        },
        {
          "url": "https://git.kernel.org/stable/c/440b003f449a4ff2a00b08c8eab9ba5cd28f3943"
        },
        {
          "url": "https://git.kernel.org/stable/c/57295e835408d8d425bef58da5253465db3d6888"
        }
      ],
      "title": "ext4: guard against EA inode refcount underflow in xattr update",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40190",
    "datePublished": "2025-11-12T21:56:30.914Z",
    "dateReserved": "2025-04-16T07:20:57.177Z",
    "dateUpdated": "2026-08-05T12:08:26.693Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.