CVE-2026-90051 (GCVE-0-2026-90051)
Vulnerability from cvelistv5
Published
2026-09-17 16:05
Modified
2026-10-19 08:57
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: tcp: reject non zerocopy devmem tx Devmem tcp tx doesn't work without zero-copy, however it's not currently enforced if NETIF_F_SG isn't present. In this case, tcp_sendmsg_locked() will try the copy path and try to copy data from an iovec which consists of offsets into the dma-buf and would normally fail. Moreover, d9c56501c72fd ("net: tcp: block mixing readable and unreadable frags") relies on that and assumes that the devmem binding is present IFF we're using the zero-copy path, which can be used to mix net-iov and pages in a single skb, and break invariants. Let's reject devmem tx without zero-copy. Note, the parameter check the patch is modifying is too loose, we can create an io_uring request with dmabuf_id and all ZC flags, but which won't have the binding. We replace it with stricter validation.
References
Impacted products
Vendor Product Version
Linux Linux Version: bd61848900bff597764238f3a8ec67c815cd316e
Version: bd61848900bff597764238f3a8ec67c815cd316e
Version: bd61848900bff597764238f3a8ec67c815cd316e
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/tcp.c"
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          "vendor": "Linux",
          "versions": [
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          "product": "Linux",
          "programFiles": [
            "net/ipv4/tcp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.16"
            },
            {
              "lessThan": "6.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.52",
                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
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                  "vulnerable": true
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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\ntcp: reject non zerocopy devmem tx\n\nDevmem tcp tx doesn\u0027t work without zero-copy, however it\u0027s not currently\nenforced if NETIF_F_SG isn\u0027t present. In this case, tcp_sendmsg_locked()\nwill try the copy path and try to copy data from an iovec which consists\nof offsets into the dma-buf and would normally fail. Moreover,\nd9c56501c72fd (\"net: tcp: block mixing readable and unreadable frags\")\nrelies on that and assumes that the devmem binding is present IFF we\u0027re\nusing the zero-copy path, which can be used to mix net-iov and pages in\na single skb, and break invariants. Let\u0027s reject devmem tx without\nzero-copy.\n\nNote, the parameter check the patch is modifying is too loose, we can\ncreate an io_uring request with dmabuf_id and all ZC flags, but which\nwon\u0027t have the binding. We replace it with stricter validation."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The triggering input is local sendmsg or io_uring IORING_OP_SENDMSG_ZC into tcp_sendmsg_locked(): SO_ZEROCOPY, MSG_ZEROCOPY, and an SCM_DEVMEM_DMABUF cmsg that sets sockc.dmabuf_id. A remote TCP peer never supplies that cmsg or those send flags; it only receives the resulting segments.\nAC:L - The attacker drives both sendmsg calls: a MSG_ZEROCOPY+SCM_DEVMEM_DMABUF send queues net-iov (unreadable) frags, then a later sendmsg with sockc.dmabuf_id while zc==0 (sk_route_caps lacks NETIF_F_SG, so the copy path runs with binding set) appends pages onto that skb. MSG_MORE retains the write-queue tail; no victim race is required.\nPR:L - NETDEV_CMD_BIND_TX has no GENL_ADMIN_PERM, and SO_ZEROCOPY plus __sock_cmsg_send(SCM_DEVMEM_DMABUF) have no capability checks. An unprivileged user can bind a TX dmabuf and reach the zc/binding check in tcp_sendmsg_locked; any extra CAP_NET_ADMIN is only the user-namespace kind.\nUI:N - The attacker enables SO_ZEROCOPY, binds a dmabuf via netdev-genl NETDEV_CMD_BIND_TX, and issues the crafted sendmsg/IORING_OP_SENDMSG_ZC sequence on their own TCP socket; no victim mount, open, or other interactive action is required.\nS:U - Mixing net_iov and page frags corrupts skb/TX processing on the sending host inside tcp_sendmsg_locked and later frag walkers. It does not cross a VM/guest or IOMMU authority; __skb_frag_dma_map still classifies each frag with skb_frag_is_net_iov.\nC:H - A mixed skb keeps skb-\u003eunreadable from skb_add_rx_frag_netmem while the zc==0 path adds page frags via skb_fill_page_desc. Walkers such as tcp_md5_hash_skb_data use skb_frag_foreach_page/skb_frag_page() on net_iovs (NULL) and kmap that pointer, enabling kernel memory disclosure.\nI:H - Appending sk_page_frag pages onto a net-iov skb via the zc==0 copy path in tcp_sendmsg_locked is frag-type confusion: TX, refcount, and skb_fill_page_desc versus skb_add_rx_frag_netmem cannot treat mixed backing consistently, which yields corrupted skb metadata and write or control-flow primitives.\nA:H - Mixed readable/unreadable frags blow up down the stack: skb_copy_bits/skb_checksum hit WARN_ON_ONCE(!skb_frags_readable), splice hits WARN_ON_ONCE(!skb_frag_page), and kmap of a NULL net_iov page oopses or panics the kernel."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:57:09.627Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2151b2bcf6fcec52665f606eed20da068447f0b7"
        },
        {
          "url": "https://git.kernel.org/stable/c/b04326c7927af7048fd4e730f5770cca350d0a60"
        },
        {
          "url": "https://git.kernel.org/stable/c/125755776bc6d4dd53eaf551c87e3d460625d638"
        }
      ],
      "title": "tcp: reject non zerocopy devmem tx",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90051",
    "datePublished": "2026-09-17T16:05:37.620Z",
    "dateReserved": "2026-09-11T19:38:34.783Z",
    "dateUpdated": "2026-10-19T08:57:09.627Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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