CVE-2026-99274 (GCVE-0-2026-99274)

Vulnerability from cvelistv5 – Published: 2026-11-07 14:08 – Updated: 2026-11-07 14:08
VLAI
Title
smb: client: fix fiemap wild read on empty truncated response
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix fiemap wild read on empty truncated response smb3_fiemap() treats -E2BIG from SMB2_ioctl() as a truncated range blob and loops for the next chunk. If the server reports STATUS_BUFFER_OVERFLOW with OutputCount == 0, SMB2_ioctl() returns -E2BIG with out_data == NULL and out_data_len == 0, and the existing length checks accept the empty result. The loop then evaluates next = out_data[num - 1].file_offset + ... with num == 0, reading 16 bytes before NULL. Reject a truncated range blob that contains no range, so the resume offset is never computed from an empty response. Also require the last range in a truncated blob to advance the resume offset without overflowing, and to stay within the requested range; a malicious or broken server could otherwise make no progress or underflow len and loop forever. Free the previous response buffer before retrying. Reproduced on 6.6.87.2 with a malicious SMB2 server that answers FSCTL_QUERY_ALLOCATED_RANGES with STATUS_BUFFER_OVERFLOW and OutputCount == 0; an FS_IOC_FIEMAP ioctl on the mount oopses in cifs_fiemap() with CR2 = fffffffffffffff8. The code path is unchanged on mainline.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6653 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 , < 4a426ca5be7e3dedbe76575b967db04fbf01136f (git)
Affected: 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 , < 31f6dbb29fe17fa9595c7e8b19fd92915b03a4ca (git)
Affected: 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 , < f5baa17a0f316c235d61623ac8e8fb32c2b3c0cc (git)
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Linux Linux Affected: 5.2
Unaffected: 0 , < 5.2 (semver)
Unaffected: 6.18.61 , ≤ 6.18.* (semver)
Unaffected: 7.3.2 , ≤ 7.3.* (semver)
Unaffected: 7.4-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
            "fs/smb/client/smb2ops.c"
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix fiemap wild read on empty truncated response\n\nsmb3_fiemap() treats -E2BIG from SMB2_ioctl() as a truncated range blob\nand loops for the next chunk. If the server reports\nSTATUS_BUFFER_OVERFLOW with OutputCount == 0, SMB2_ioctl() returns\n-E2BIG with out_data == NULL and out_data_len == 0, and the existing\nlength checks accept the empty result. The loop then evaluates\n\n\tnext = out_data[num - 1].file_offset + ...\n\nwith num == 0, reading 16 bytes before NULL.\n\nReject a truncated range blob that contains no range, so the resume\noffset is never computed from an empty response. Also require the last\nrange in a truncated blob to advance the resume offset without\noverflowing, and to stay within the requested range; a malicious or\nbroken server could otherwise make no progress or underflow len and loop\nforever. Free the previous response buffer before retrying.\n\nReproduced on 6.6.87.2 with a malicious SMB2 server that answers\nFSCTL_QUERY_ALLOCATED_RANGES with STATUS_BUFFER_OVERFLOW and\nOutputCount == 0; an FS_IOC_FIEMAP ioctl on the mount oopses in\ncifs_fiemap() with CR2 = fffffffffffffff8. The code path is unchanged\non mainline."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-07T14:08:45.924Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/4a426ca5be7e3dedbe76575b967db04fbf01136f"
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          "url": "https://git.kernel.org/stable/c/31f6dbb29fe17fa9595c7e8b19fd92915b03a4ca"
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        {
          "url": "https://git.kernel.org/stable/c/f5baa17a0f316c235d61623ac8e8fb32c2b3c0cc"
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      "title": "smb: client: fix fiemap wild read on empty truncated response",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99274",
    "datePublished": "2026-11-07T14:08:45.924Z",
    "dateReserved": "2026-09-25T10:25:14.405Z",
    "dateUpdated": "2026-11-07T14:08:45.924Z",
    "state": "PUBLISHED"
  },
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix fiemap wild read on empty truncated response\n\nsmb3_fiemap() treats -E2BIG from SMB2_ioctl() as a truncated range blob\nand loops for the next chunk. If the server reports\nSTATUS_BUFFER_OVERFLOW with OutputCount == 0, SMB2_ioctl() returns\n-E2BIG with out_data == NULL and out_data_len == 0, and the existing\nlength checks accept the empty result. The loop then evaluates\n\n\tnext = out_data[num - 1].file_offset + ...\n\nwith num == 0, reading 16 bytes before NULL.\n\nReject a truncated range blob that contains no range, so the resume\noffset is never computed from an empty response. Also require the last\nrange in a truncated blob to advance the resume offset without\noverflowing, and to stay within the requested range; a malicious or\nbroken server could otherwise make no progress or underflow len and loop\nforever. Free the previous response buffer before retrying.\n\nReproduced on 6.6.87.2 with a malicious SMB2 server that answers\nFSCTL_QUERY_ALLOCATED_RANGES with STATUS_BUFFER_OVERFLOW and\nOutputCount == 0; an FS_IOC_FIEMAP ioctl on the mount oopses in\ncifs_fiemap() with CR2 = fffffffffffffff8. The code path is unchanged\non mainline."
          }
        ],
        "id": "CVE-2026-99274",
        "lastModified": "2026-11-07T14:17:02.730",
        "metrics": {},
        "published": "2026-11-07T14:17:02.730",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          }
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-11-07T20:45:31+00:00",
      "cve": "CVE-2026-99274",
      "id": "CVE-2026-99274",
      "initial_release_date": "2026-11-07T14:08:45.924000+00:00",
      "product_status:known_affected": "162",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: kernel: Denial of service via empty truncated responses in SMB client",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-99274.json",
      "version": "3"
    }
  }
}



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