CVE-2026-74315 (GCVE-0-2026-74315)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:58 – Updated: 2026-08-17 05:45
VLAI
Title
lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file()
Summary
In the Linux kernel, the following vulnerability has been resolved: lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file() file_hash() digests the first LOCKD_FH_HASH_SIZE bytes of nfs_fh.data when bucketing nlm_files[], independent of fh.size. Commit 3de744ee4e45 ("lockd: Use xdrgen XDR functions for the NLMv4 TEST procedure") set .pc_argzero to zero for the converted procedures and moved file-handle population into nlm4svc_lookup_file(), which copies only xdr_lock->fh.len bytes into lock->fh.data. When an NLMv4 client presents a file handle shorter than LOCKD_FH_HASH_SIZE, bytes fh.len..31 retain whatever the argument buffer held from an earlier request. The same wire handle then hashes to different buckets across calls; nlm_lookup_file() misses the existing nlm_file entry, and lock-state lookups fail. Zero only the tail bytes that file_hash() would otherwise consume. Handles of LOCKD_FH_HASH_SIZE or larger already populate every byte that file_hash() reads.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 3de744ee4e4557da0d63be8a97ad44b4dad58912 , < 686c2434f9f16b87aeed18d76cc562df9f2695ab (git)
Affected: 3de744ee4e4557da0d63be8a97ad44b4dad58912 , < 6e4c62caecf792e8a15ad9bc7f371e57c17e3302 (git)
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Linux Linux Affected: 7.1
Unaffected: 0 , < 7.1 (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/lockd/lockd.h",
            "fs/lockd/svc4proc.c",
            "fs/lockd/svcsubs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "686c2434f9f16b87aeed18d76cc562df9f2695ab",
              "status": "affected",
              "version": "3de744ee4e4557da0d63be8a97ad44b4dad58912",
              "versionType": "git"
            },
            {
              "lessThan": "6e4c62caecf792e8a15ad9bc7f371e57c17e3302",
              "status": "affected",
              "version": "3de744ee4e4557da0d63be8a97ad44b4dad58912",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/lockd/lockd.h",
            "fs/lockd/svc4proc.c",
            "fs/lockd/svcsubs.c"
          ],
          "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\nlockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file()\n\nfile_hash() digests the first LOCKD_FH_HASH_SIZE bytes of\nnfs_fh.data when bucketing nlm_files[], independent of fh.size.\nCommit 3de744ee4e45 (\"lockd: Use xdrgen XDR functions for the\nNLMv4 TEST procedure\") set .pc_argzero to zero for the converted\nprocedures and moved file-handle population into\nnlm4svc_lookup_file(), which copies only xdr_lock-\u003efh.len bytes\ninto lock-\u003efh.data.\n\nWhen an NLMv4 client presents a file handle shorter than\nLOCKD_FH_HASH_SIZE, bytes fh.len..31 retain whatever the argument\nbuffer held from an earlier request.  The same wire handle then\nhashes to different buckets across calls; nlm_lookup_file() misses\nthe existing nlm_file entry, and lock-state lookups fail.\n\nZero only the tail bytes that file_hash() would otherwise consume.\nHandles of LOCKD_FH_HASH_SIZE or larger already populate every byte\nthat file_hash() reads."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug is reached via remote NLMv4 RPC to in-kernel lockd (TCP/UDP SunRPC, typically alongside nfsd), from svc_process() through nlm4svc_proc_* handlers into nlm4svc_lookup_file() and nlm_lookup_file().\nAC:L - An NFS client can reliably trigger this by sending NLMv4 LOCK/TEST/SHARE/etc. with a file handle shorter than 32 bytes; stale tail bytes come from the same worker\u0027s prior RPC argument buffer, which the attacker can influence with earlier requests.\nPR:N - lockd_authenticate() accepts RPC_AUTH_NULL/RPC_AUTH_UNIX and, for normal procedures, svc_set_client(); no local UID, capabilities, or root in the host namespace is required\u2014only network reachability as an NFS export client (AUTH_NULL is explicitly supported for NLM).\nUI:N - Exploitation requires only crafted NLMv4 RPC traffic to a running lockd/nfsd instance; no victim mount, file open, or other interactive action beyond normal NFS client participation.\nS:U - Impact is confined to the NFS server\u0027s kernel lockd/nfsd authority (file-lock and DOS-share state on exported files); it does not cross VM, container, or IOMMU security boundaries.\nC:H - file_hash() sums the first 32 bytes of nfs_fh.data regardless of fh.size; when fh.len\u003c32, bytes fh.len..31 are stale prior-request buffer contents, so each lookup performs an out-of-bounds read of up to 31 bytes used in security-relevant file-table indexing.\nI:H - Inconsistent hashing creates duplicate nlm_file entries for the same wire handle; per-entry f_shares and nlm_block state diverge while both open the same inode, enabling DOS share-mode bypass and incorrect lock/block bookkeeping despite VFS-level enforcement.\nA:H - Missed nlm_file lookups cause lock-state lookup failures, incorrect NLM responses, hung or failing NFS lock clients, and unbounded duplicate nlm_file/VFS opens that can exhaust server lock-manager resources on production NFS file servers."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:45:48.282Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/686c2434f9f16b87aeed18d76cc562df9f2695ab"
        },
        {
          "url": "https://git.kernel.org/stable/c/6e4c62caecf792e8a15ad9bc7f371e57c17e3302"
        }
      ],
      "title": "lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74315",
    "datePublished": "2026-08-15T05:58:13.504Z",
    "dateReserved": "2026-08-15T05:44:03.883Z",
    "dateUpdated": "2026-08-17T05:45:48.282Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-74315",
      "date": "2026-09-21",
      "epss": "0.0038",
      "percentile": "0.31732"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "fs/lockd/lockd.h",
                  "fs/lockd/svc4proc.c",
                  "fs/lockd/svcsubs.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "lessThan": "686c2434f9f16b87aeed18d76cc562df9f2695ab",
                    "status": "affected",
                    "version": "3de744ee4e4557da0d63be8a97ad44b4dad58912",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "6e4c62caecf792e8a15ad9bc7f371e57c17e3302",
                    "status": "affected",
                    "version": "3de744ee4e4557da0d63be8a97ad44b4dad58912",
                    "versionType": "git"
                  }
                ]
              },
              {
                "defaultStatus": "affected",
                "product": "Linux",
                "programFiles": [
                  "fs/lockd/lockd.h",
                  "fs/lockd/svc4proc.c",
                  "fs/lockd/svcsubs.c"
                ],
                "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"
                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file()\n\nfile_hash() digests the first LOCKD_FH_HASH_SIZE bytes of\nnfs_fh.data when bucketing nlm_files[], independent of fh.size.\nCommit 3de744ee4e45 (\"lockd: Use xdrgen XDR functions for the\nNLMv4 TEST procedure\") set .pc_argzero to zero for the converted\nprocedures and moved file-handle population into\nnlm4svc_lookup_file(), which copies only xdr_lock-\u003efh.len bytes\ninto lock-\u003efh.data.\n\nWhen an NLMv4 client presents a file handle shorter than\nLOCKD_FH_HASH_SIZE, bytes fh.len..31 retain whatever the argument\nbuffer held from an earlier request.  The same wire handle then\nhashes to different buckets across calls; nlm_lookup_file() misses\nthe existing nlm_file entry, and lock-state lookups fail.\n\nZero only the tail bytes that file_hash() would otherwise consume.\nHandles of LOCKD_FH_HASH_SIZE or larger already populate every byte\nthat file_hash() reads."
          }
        ],
        "id": "CVE-2026-74315",
        "lastModified": "2026-08-17T06:19:25.867",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-08-15T06:22:31.763",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/686c2434f9f16b87aeed18d76cc562df9f2695ab"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/6e4c62caecf792e8a15ad9bc7f371e57c17e3302"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-20T17:18:34+00:00",
      "cve": "CVE-2026-74315",
      "id": "CVE-2026-74315",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74315.json",
      "version": "3"
    }
  }
}



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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

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  • 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.


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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.