GHSA-7XVH-M494-6W6X

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

openvswitch: only skb_tx_error() a packet we are about to drop

queue_userspace_packet() borrows the packet skb -- it only copies it into a private netlink message (user_skb) and does not own it; on return do_execute_actions() keeps forwarding it through the flow's remaining actions. Its error path nevertheless calls skb_tx_error(skb), which via skb_zcopy_clear() does skb_shinfo(skb)->flags &= ~SKBFL_ALL_ZEROCOPY, stripping SKBFL_SHARED_FRAG from that live skb (skb_tx_error()'s kerneldoc says "skb must be freed afterwards").

For a MSG_ZEROCOPY skb carrying page-cache frags, SKBFL_SHARED_FRAG is what makes esp_input() skb_cow_data() before in-place AEAD; once it is stripped a later local ESP-in-UDP delivery decrypts in place over pages the sender does not own -- an unprivileged page-cache write (the "Fragnesia" primitive). do_execute_actions() ignores output_userspace()'s return value, so any action after a failed USERSPACE upcall inherits the stripped skb.

Move the skb_tx_error() to the flow-miss drop path - the "default" branch of ovs_dp_process_packet()'s switch(error), before kfree_skb().

The call has been here since commit 36d5fe6a0007 ("core, nfqueue, openvswitch: Orphan frags in skb_zerocopy and handle errors") but was harmless until esp_input() began relying on SKBFL_SHARED_FRAG to gate in-place decrypt; only then did stripping it on a still-forwarded skb become a page-cache write primitive.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-89487"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:30Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nopenvswitch: only skb_tx_error() a packet we are about to drop\n\nqueue_userspace_packet() borrows the packet skb -- it only copies it into\na private netlink message (user_skb) and does not own it; on return\ndo_execute_actions() keeps forwarding it through the flow\u0027s remaining\nactions. Its error path nevertheless calls skb_tx_error(skb), which via\nskb_zcopy_clear() does skb_shinfo(skb)-\u003eflags \u0026= ~SKBFL_ALL_ZEROCOPY,\nstripping SKBFL_SHARED_FRAG from that live skb (skb_tx_error()\u0027s kerneldoc\nsays \"skb must be freed afterwards\").\n\nFor a MSG_ZEROCOPY skb carrying page-cache frags, SKBFL_SHARED_FRAG is\nwhat makes esp_input() skb_cow_data() before in-place AEAD; once it is\nstripped a later local ESP-in-UDP delivery decrypts in place over pages\nthe sender does not own -- an unprivileged page-cache write (the\n\"Fragnesia\" primitive).\ndo_execute_actions() ignores output_userspace()\u0027s return value, so any\naction after a failed USERSPACE upcall inherits the stripped skb.\n\nMove the skb_tx_error() to the flow-miss drop path - the \"default\"\nbranch of ovs_dp_process_packet()\u0027s switch(error), before kfree_skb().\n\nThe call has been here since commit 36d5fe6a0007 (\"core, nfqueue,\nopenvswitch: Orphan frags in skb_zerocopy and handle errors\") but was\nharmless until esp_input() began relying on SKBFL_SHARED_FRAG to gate\nin-place decrypt; only then did stripping it on a still-forwarded skb\nbecome a page-cache write primitive.",
  "id": "GHSA-7xvh-m494-6w6x",
  "modified": "2026-09-14T15:32:26Z",
  "published": "2026-09-11T21:31:28Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89487"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0dbc2398fca3bb33eda963849f865ddb1b3aa05e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4477222e2916a18e273edc139c955ade6bbb7a69"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/48db11e115d1b232edc5591604adc6eda95cd545"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4d5c460ef8754be1d43b16dbf02695b008b207d6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5d85eef222cfd28e73deed7402c100229e8b9e6e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5de5d554141a15b3f1f5c978fd9f7f4fd6d0600a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6767d70cf46f65807a6a4c4406a518e6c12e36ae"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e41a59fc056f63a7a1f42788913c53cc48d744aa"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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