CVE-2026-63830 (GCVE-0-2026-63830)
Vulnerability from cvelistv5
Published
2026-07-19 12:02
Modified
2026-08-17 04:51
Severity ?
9.4 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Summary
In the Linux kernel, the following vulnerability has been resolved: net: skmsg: preserve sg.copy across SG transforms The sk_msg sg.copy bitmap is part of the scatterlist entry ownership state. A set bit tells sk_msg_compute_data_pointers() not to expose the entry through writable BPF ctx->data. This protects entries backed by pages that are not private to the sk_msg, such as splice-backed file page-cache pages. Several sk_msg transform paths move, copy, split, or compact msg->sg.data[] entries without moving the matching sg.copy bit. This can make an externally backed entry arrive at a new slot with a clear copy bit. A later SK_MSG verdict can then expose sg_virt(sge) as writable ctx->data and BPF stores can modify the original page cache. Keep sg.copy synchronized with sg.data[] whenever entries are transferred, shifted, split, or copied into a new sk_msg. Clear the bit when an entry is replaced by a newly allocated private page or freed. This covers the BPF pull/push/pop helpers, sk_msg_shift_left/right(), sk_msg_xfer(), and tls_split_open_record(), including the partial tail entry created during TLS open-record splitting.
References
Impacted products
Vendor Product Version
Linux Linux Version: d3b18ad31f93d0b6bae105c679018a1ba7daa9ca
Version: d3b18ad31f93d0b6bae105c679018a1ba7daa9ca
Version: d3b18ad31f93d0b6bae105c679018a1ba7daa9ca
Version: d3b18ad31f93d0b6bae105c679018a1ba7daa9ca
Version: d3b18ad31f93d0b6bae105c679018a1ba7daa9ca
Version: d3b18ad31f93d0b6bae105c679018a1ba7daa9ca
Version: d3b18ad31f93d0b6bae105c679018a1ba7daa9ca
Version: d3b18ad31f93d0b6bae105c679018a1ba7daa9ca
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/linux/skmsg.h",
            "net/core/filter.c",
            "net/core/skmsg.c",
            "net/tls/tls_sw.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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        },
        {
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          "product": "Linux",
          "programFiles": [
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            "net/core/filter.c",
            "net/core/skmsg.c",
            "net/tls/tls_sw.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "4.20"
            },
            {
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
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              "version": "5.10.261",
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            },
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              "status": "unaffected",
              "version": "5.15.212",
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            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.177",
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            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.144",
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              "status": "unaffected",
              "version": "6.12.95",
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              "status": "unaffected",
              "version": "6.18.38",
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            {
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              "status": "unaffected",
              "version": "7.1.3",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.261",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
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                  "versionEndExcluding": "5.15.212",
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                  "vulnerable": true
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                  "vulnerable": true
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                {
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              ],
              "negate": false,
              "operator": "OR"
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          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: skmsg: preserve sg.copy across SG transforms\n\nThe sk_msg sg.copy bitmap is part of the scatterlist entry ownership\nstate. A set bit tells sk_msg_compute_data_pointers() not to expose the\nentry through writable BPF ctx-\u003edata. This protects entries backed by\npages that are not private to the sk_msg, such as splice-backed file\npage-cache pages.\n\nSeveral sk_msg transform paths move, copy, split, or compact\nmsg-\u003esg.data[] entries without moving the matching sg.copy bit. This can\nmake an externally backed entry arrive at a new slot with a clear copy\nbit. A later SK_MSG verdict can then expose sg_virt(sge) as writable\nctx-\u003edata and BPF stores can modify the original page cache.\n\nKeep sg.copy synchronized with sg.data[] whenever entries are\ntransferred, shifted, split, or copied into a new sk_msg. Clear the bit\nwhen an entry is replaced by a newly allocated private page or freed.\nThis covers the BPF pull/push/pop helpers, sk_msg_shift_left/right(),\nsk_msg_xfer(), and tls_split_open_record(), including the partial tail\nentry created during TLS open-record splitting."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.4,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug is exercised on the kTLS/TCP send path when splice-backed page-cache pages in an sk_msg are processed by an SK_MSG BPF verdict on network sockets; a remote TLS peer can trigger this on internet-facing servers (HTTPS, service-mesh edge nodes) that serve file-backed responses via splice/sendfile.\nAC:L - The attacker controls the traffic patterns, message sizes, and splice-backed data needed to hit the desynchronized transform paths (bpf_msg_push/pop/pull, sk_msg shift/xfer, tls_split_open_record); no race against unrelated system state is required.\nPR:N - On production kTLS servers with an attached SK_MSG BPF program (common in Cilium/Cloudflare-class deployments), an unauthenticated remote peer can trigger the faulty transforms without any credentials on the victim; a fully local exploit via user-namespace CAP_NET_ADMIN is also possible but is not the highest-severity case.\nUI:N - Exploitation requires only network traffic to a vulnerable server (or local socket I/O); no victim user action such as opening a file or mounting a filesystem is needed beyond normal server operation.\nS:U - Impact remains within the kernel\u0027s security authority (page-cache corruption via the network/BPF stack); it does not cross a VM-hypervisor or IOMMU boundary even though corrupted cache pages may affect other processes.\nC:H - Exposing splice-backed page-cache pages as writable BPF ctx-\u003edata gives the attacker a kernel memory write primitive over shared file cache pages, which can be leveraged to read or infer sensitive file contents served from or mapped through the corrupted pages.\nI:H - The commit explicitly states BPF stores through the incorrectly writable ctx-\u003edata can modify the original page cache, constituting arbitrary integrity corruption of file-backed data beyond the socket buffer.\nA:L - While the primary impact is data corruption rather than a kernel oops, corrupting shared page-cache pages of files actively served to other clients can cause sustained service disruption and repeated application-level failures; when uncertain, availability impact above None is appropriate."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:51:39.075Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f126eed589eec6f201405abbc398844042ef6d57"
        },
        {
          "url": "https://git.kernel.org/stable/c/31a110642b5fb5e61940cbcfb503445ac4f28017"
        },
        {
          "url": "https://git.kernel.org/stable/c/9bb86d8184b37503816150c4a6ad3c17dfdbe827"
        },
        {
          "url": "https://git.kernel.org/stable/c/0eb4c16c4adb262763bda870a8ed38a1a9dec7ec"
        },
        {
          "url": "https://git.kernel.org/stable/c/d22cc92bc41290e5783a72375e0843d9435f6001"
        },
        {
          "url": "https://git.kernel.org/stable/c/1acdd14c0990dd1cd4b6534f00366d2e6dfce05f"
        },
        {
          "url": "https://git.kernel.org/stable/c/21ed9540a8e1906dfcbc1bb82ba9b4de4fa4bd6d"
        },
        {
          "url": "https://git.kernel.org/stable/c/406e8a651a7b854c41fecd5117bb282b3a6c2c6b"
        }
      ],
      "title": "net: skmsg: preserve sg.copy across SG transforms",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63830",
    "datePublished": "2026-07-19T12:02:23.741Z",
    "dateReserved": "2026-07-19T07:54:57.014Z",
    "dateUpdated": "2026-08-17T04:51:39.075Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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