Vulnerability-Lookup

GHSA-HWFC-7PP7-M5J3

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32

Details

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

cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0

With len == 0 (clone to EOF), the effective length is computed as:

len = src_inode->i_size - off;

If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent.

Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep().

Severity

7.1 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-89640"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:49Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: fix loff_t underflow in cifs_remap_file_range() when len == 0\n\nWith len == 0 (clone to EOF), the effective length is computed as:\n\n    len = src_inode-\u003ei_size - off;\n\nIf off \u003e i_size, this is a negative loff_t, corrupting the ByteCount\nin the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range\nin filemap_write_and_wait_range().  The existing off \u003e= i_size check\nfires only after the ioctl has already been sent.\n\nSnapshot i_size_read() once for both the bounds check and the length\ncalculation, eliminating the TOCTOU and 32-bit torn-read risk.  Reject\noff \u003e src_size with -EINVAL.  Treat off == src_size as a no-op,\nconsistent with __generic_remap_file_range_prep().",
  "id": "GHSA-hwfc-7pp7-m5j3",
  "modified": "2026-09-14T15:32:32Z",
  "published": "2026-09-11T21:31:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89640"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7f62817fe049b0f3652518c1ba72631ec1e0a322"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b098f5e5858797827666e6cd73033f52fc39b5f6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-89640 (GCVE-0-2026-89640)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:45 – Updated: 2026-09-14 12:01

Title

cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0

Summary

In the Linux kernel, the following vulnerability has been resolved: cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 With len == 0 (clone to EOF), the effective length is computed as: len = src_inode->i_size - off; If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent. Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep().

Severity

7.1 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Assigner

Linux mitre root

References

6 references

URL	Tags
https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f55…
https://git.kernel.org/stable/c/7f62817fe049b0f36…
https://git.kernel.org/stable/c/b098f5e5858797827…
https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa…
https://git.kernel.org/stable/c/b057ca17b656345d0…
https://git.kernel.org/stable/c/6c322f5cf7476ded7…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 04b38d601239b4d9be641b412cf4b7456a041c67 , < f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4 (git) Affected: 04b38d601239b4d9be641b412cf4b7456a041c67 , < 7f62817fe049b0f3652518c1ba72631ec1e0a322 (git) Affected: 04b38d601239b4d9be641b412cf4b7456a041c67 , < b098f5e5858797827666e6cd73033f52fc39b5f6 (git) Affected: 04b38d601239b4d9be641b412cf4b7456a041c67 , < c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028 (git) Affected: 04b38d601239b4d9be641b412cf4b7456a041c67 , < b057ca17b656345d04669cb87f2aff9b31d873db (git) Affected: 04b38d601239b4d9be641b412cf4b7456a041c67 , < 6c322f5cf7476ded7a9a20f7be72462065a03c68 (git)
Linux	Linux	Affected: 4.5 Unaffected: 0 , < 4.5 (semver) Unaffected: 6.1.188 , ≤ 6.1.* (semver) Unaffected: 6.6.157 , ≤ 6.6.* (semver) Unaffected: 6.12.109 , ≤ 6.12.* (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/cifsfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4",
              "status": "affected",
              "version": "04b38d601239b4d9be641b412cf4b7456a041c67",
              "versionType": "git"
            },
            {
              "lessThan": "7f62817fe049b0f3652518c1ba72631ec1e0a322",
              "status": "affected",
              "version": "04b38d601239b4d9be641b412cf4b7456a041c67",
              "versionType": "git"
            },
            {
              "lessThan": "b098f5e5858797827666e6cd73033f52fc39b5f6",
              "status": "affected",
              "version": "04b38d601239b4d9be641b412cf4b7456a041c67",
              "versionType": "git"
            },
            {
              "lessThan": "c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028",
              "status": "affected",
              "version": "04b38d601239b4d9be641b412cf4b7456a041c67",
              "versionType": "git"
            },
            {
              "lessThan": "b057ca17b656345d04669cb87f2aff9b31d873db",
              "status": "affected",
              "version": "04b38d601239b4d9be641b412cf4b7456a041c67",
              "versionType": "git"
            },
            {
              "lessThan": "6c322f5cf7476ded7a9a20f7be72462065a03c68",
              "status": "affected",
              "version": "04b38d601239b4d9be641b412cf4b7456a041c67",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/cifsfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.5"
            },
            {
              "lessThan": "4.5",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
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              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "4.5",
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                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: fix loff_t underflow in cifs_remap_file_range() when len == 0\n\nWith len == 0 (clone to EOF), the effective length is computed as:\n\n    len = src_inode-\u003ei_size - off;\n\nIf off \u003e i_size, this is a negative loff_t, corrupting the ByteCount\nin the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range\nin filemap_write_and_wait_range().  The existing off \u003e= i_size check\nfires only after the ioctl has already been sent.\n\nSnapshot i_size_read() once for both the bounds check and the length\ncalculation, eliminating the TOCTOU and 32-bit torn-read risk.  Reject\noff \u003e src_size with -EINVAL.  Treat off == src_size as a no-op,\nconsistent with __generic_remap_file_range_prep()."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is in the CIFS client remap method, reached from the local FICLONERANGE/FICLONE ioctls through vfs_clone_file_range() on an already-mounted CIFS share, not from SMB packet parsing in ksmbd or the TCP stack.\nAC:L - An attacker fully controls src_offset and src_length and can set length to 0 with offset past i_size, so the loff_t underflow is deterministic and does not depend on a race or memory layout they cannot influence.\nPR:L - vfs_clone_file_range() only requires a regular source opened for read and a regular destination opened for write; any unprivileged user with those fds on a CIFS mount can issue FICLONERANGE without capabilities or init-namespace root.\nUI:N - The attacker opens their own CIFS files and issues the ioctl; no separate victim action such as mounting a share or opening a file is required once a typical enterprise/autofs CIFS mount exists.\nS:U - Impact stays inside the host kernel and the CIFS inode/page cache of the same OS security authority; this is not a VM, IOMMU, or sandbox boundary crossing.\nC:N - The underflow does not read attacker-inaccessible kernel or file data; it miscomputes a clone length and then truncates destination page cache and sends a bad FSCTL, with no out-of-bounds or UAF read primitive.\nI:H - Negative len wraps destend to a huge uoff_t so truncate_inode_pages_range() discards the destination file\u0027s page cache, including dirty folios not flushed in the inverted range, silently destroying buffered data, and the same value corrupts ByteCount in FSCTL_DUPLICATE_EXTENTS_TO_FILE.\nA:H - The same wrapped range and signed-to-u64 conversion can set a huge/negative EOF via smb2_set_file_size()/cifs_resize_file_locked() on duplicate-extents servers and leave netfs/pagecache state inconsistent, which can oops, hang, or deny access to the affected file and kernel paths."
            }
          ]
        }
      ],
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        "dateUpdated": "2026-09-14T12:01:42.820Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        },
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        },
        {
          "url": "https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db"
        },
        {
          "url": "https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68"
        }
      ],
      "title": "cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0",
      "x_generator": {
        "engine": "bippy-1.2.0"
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89640",
    "datePublished": "2026-09-11T19:45:33.289Z",
    "dateReserved": "2026-09-11T19:38:34.740Z",
    "dateUpdated": "2026-09-14T12:01:42.820Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

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