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CVE-2026-72217 (GCVE-0-2026-72217)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:54 – Updated: 2026-08-17 05:41
VLAI
Title
SUNRPC: Bound-check xdr_buf_to_bvec() stores before writing
Summary
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Bound-check xdr_buf_to_bvec() stores before writing xdr_buf_to_bvec() writes a bio_vec into the caller's array before testing whether that slot is in range, and the head branch performs the store with no check at all. When the caller's budget is exactly used up, the next store lands one element past the end of the array. The overflow label returns count - 1, which masks the surplus store but cannot undo it. rq_bvec, the array passed by nfsd_vfs_write(), is allocated to exactly rq_maxpages entries with no slack. The OOB store can land in adjacent slab memory; the bv_len and bv_offset fields written there are derived from client-supplied RPC payload sizes. Move the in-range check ahead of the store in the head, page-loop, and tail branches. With the check at the top of each sequence, count is incremented only after a successful store, so the overflow label can return count directly.
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: 2eb2b93581813b74c7174961126f6ec38eadb5a7 , < 4a1148f2739d5089c3ca8ae2e9d1053e219ab5df (git)
Affected: 2eb2b93581813b74c7174961126f6ec38eadb5a7 , < 6029e711a818bf34d6c4b90cafee24f3afffa110 (git)
Affected: 2eb2b93581813b74c7174961126f6ec38eadb5a7 , < 69e18135e2a004a79505451dbef07314ea16e1eb (git)
Affected: 2eb2b93581813b74c7174961126f6ec38eadb5a7 , < 98414b42530af65cb984ffc12685096a3b5e179a (git)
Affected: 2eb2b93581813b74c7174961126f6ec38eadb5a7 , < 42f5b80dda6b86e424054baf1475df686c403d5c (git)
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Linux Linux Affected: 6.6
Unaffected: 0 , < 6.6 (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: Bound-check xdr_buf_to_bvec() stores before writing\n\nxdr_buf_to_bvec() writes a bio_vec into the caller\u0027s array before\ntesting whether that slot is in range, and the head branch performs\nthe store with no check at all. When the caller\u0027s budget is exactly\nused up, the next store lands one element past the end of the array.\nThe overflow label returns count - 1, which masks the surplus store\nbut cannot undo it.\n\nrq_bvec, the array passed by nfsd_vfs_write(), is allocated to\nexactly rq_maxpages entries with no slack. The OOB store can land in\nadjacent slab memory; the bv_len and bv_offset fields written there\nare derived from client-supplied RPC payload sizes.\n\nMove the in-range check ahead of the store in the head, page-loop,\nand tail branches. With the check at the top of each sequence, count\nis incremented only after a successful store, so the overflow label\ncan return count directly."
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              "value": "AV:N - Remote attackers reach xdr_buf_to_bvec() through network-facing nfsd SUNRPC on TCP/UDP port 2049 (and NFS/RDMA transports); a crafted NFS WRITE RPC supplies the xdr_buf processed by nfsd4_write()/nfsd_proc_write() into nfsd_vfs_write().\nAC:L - The attacker controls NFS WRITE payload size and RPC record layout to exhaust the rq_bvec bio_vec budget; the one-element out-of-bounds store is a deterministic protocol craft, not a race or memory-layout condition outside attacker control.\nPR:N - No local shell or init-namespace root is required; a remote NFS client with export write permission (typical AUTH_UNIX/AUTH_NULL mappings on misconfigured or permissive exports) can issue crafted WRITE requests after normal NFS open/stateid setup.\nUI:N - Exploitation requires only attacker-initiated NFS RPC traffic to an exposed nfsd instance; no separate victim must mount shares, open files, or perform other interactive actions beyond the attacker operating their own client.\nS:U - Impact is a kernel heap out-of-bounds write adjacent to the per-thread rq_bvec kmalloc array during nfsd request handling; this enables privilege escalation on the NFS server host but does not cross VM, container, or IOMMU security boundaries.\nC:H - The overflow stores a full bio_vec (page pointer plus attacker-controlled bv_len and bv_offset derived from client RPC payload sizes) into adjacent slab memory; such heap corruption can disclose kernel memory and is not a bounded benign leak.\nI:H - Attacker-controlled bio_vec fields are written past the end of rq_bvec into adjacent kernel heap objects, providing a memory-corruption primitive that can be developed into arbitrary kernel writes and code execution, not merely limited data alteration.\nA:H - The extraneous store corrupts adjacent slab memory; on vulnerable kernels the overflow path returned count-1 without aborting nfsd_vfs_write(), so servers can kernel oops, panic, or hang during or after malformed writes even before full exploitation."
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    "datePublished": "2026-08-15T05:54:10.888Z",
    "dateReserved": "2026-08-09T03:40:39.913Z",
    "dateUpdated": "2026-08-17T05:41:40.504Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-08-18T16:27:44+00:00",
      "cve": "CVE-2026-72217",
      "id": "CVE-2026-72217",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "184",
      "product_status:under_investigation": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: SUNRPC: Bound-check xdr_buf_to_bvec() stores before writing",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72217.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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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.