FKIE_CVE-2026-89704

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-10-19 09:18
Severity
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: sample writeback error cursor before async COPY loop _nfsd_copy_file_range() samples dst->f_wb_err into "since" after the copy loop, then uses it to detect writeback errors via filemap_check_wb_err() once vfs_fsync_range() returns. Because the nfsd_file cache reuses a single struct file across requests targeting the same inode, a concurrent COMMIT or stable WRITE on dst advances dst->f_wb_err to the current mapping->wb_err via file_check_and_advance_wb_err() during its own vfs_fsync_range(). If that advancement lands between the writeback error appearing in mapping->wb_err and the COPY worker sampling "since", the worker captures the already-advanced cursor, errseq_check() sees cur == since and returns zero, and NFSD4_COPY_F_COMMITTED is set even though writeback failed. CB_OFFLOAD then encodes wr_stable_how = FILE_SYNC4, the client treats the copied data as durable, and the failure becomes silent data loss. Sample since once at the start of the function. The cursor then reflects state in effect before this COPY issues any writes, and filemap_check_wb_err() detects any error that occurs during the copy regardless of which thread first observes it. This matches the pattern used by nfsd_vfs_write() and nfsd4_clone_file_range().
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/322422d66d1a04434a0dcc0c9d3a4c4b3f225117
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/435e4246c7dfff2fbd76dfdbf91975d5d9f788c9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4728504c021656128a07f4693af80ed4a5fcc863
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9f539a1c0791f907eb4e6d04b43178d9962e2def
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "435e4246c7dfff2fbd76dfdbf91975d5d9f788c9",
              "status": "affected",
              "version": "f14816f2f928c560d28ba344af689f56efcd6f55",
              "versionType": "git"
            },
            {
              "lessThan": "9f539a1c0791f907eb4e6d04b43178d9962e2def",
              "status": "affected",
              "version": "3145fe0ebb16e1715ad541a301bc6675c8375fcd",
              "versionType": "git"
            },
            {
              "lessThan": "4728504c021656128a07f4693af80ed4a5fcc863",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "322422d66d1a04434a0dcc0c9d3a4c4b3f225117",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "52b2db7a72e19ac2686fa4b2a52406661e7bf9e2",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "8277d4a11ae2cb5495842be558fd946032c24363",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "a1cbafe756cd5e6ab0e099062f37da7a5b081169",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "20a67a7d18221af736f124770c2c5e859b479046",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "5.10.270",
              "status": "affected",
              "version": "5.10.124",
              "versionType": "semver"
            },
            {
              "lessThan": "5.15.221",
              "status": "affected",
              "version": "5.15.49",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.17"
            },
            {
              "lessThan": "5.17",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: sample writeback error cursor before async COPY loop\n\n_nfsd_copy_file_range() samples dst-\u003ef_wb_err into \"since\"\nafter the copy loop, then uses it to detect writeback errors\nvia filemap_check_wb_err() once vfs_fsync_range() returns.\nBecause the nfsd_file cache reuses a single struct file\nacross requests targeting the same inode, a concurrent\nCOMMIT or stable WRITE on dst advances dst-\u003ef_wb_err to the\ncurrent mapping-\u003ewb_err via file_check_and_advance_wb_err()\nduring its own vfs_fsync_range(). If that advancement lands\nbetween the writeback error appearing in mapping-\u003ewb_err\nand the COPY worker sampling \"since\", the worker captures\nthe already-advanced cursor, errseq_check() sees cur ==\nsince and returns zero, and NFSD4_COPY_F_COMMITTED is set\neven though writeback failed. CB_OFFLOAD then encodes\nwr_stable_how = FILE_SYNC4, the client treats the copied\ndata as durable, and the failure becomes silent data loss.\n\nSample since once at the start of the function. The cursor\nthen reflects state in effect before this COPY issues any\nwrites, and filemap_check_wb_err() detects any error that\noccurs during the copy regardless of which thread first\nobserves it. This matches the pattern used by\nnfsd_vfs_write() and nfsd4_clone_file_range()."
    }
  ],
  "id": "CVE-2026-89704",
  "lastModified": "2026-10-19T09:18:09.080",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:19:57.657",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/322422d66d1a04434a0dcc0c9d3a4c4b3f225117"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/435e4246c7dfff2fbd76dfdbf91975d5d9f788c9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4728504c021656128a07f4693af80ed4a5fcc863"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9f539a1c0791f907eb4e6d04b43178d9962e2def"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Loading timeline…




    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.